You're not going to end with belief in the the trinity doctrine after you read the Bible if you don't already start off with the preconceived idea of a trinity. Try this, write down the definition of the trinity then read the Bible starting from Genesis and see where the first verse is that records that definition.

(Colossians 2:8) Look out that no one takes you captive by means of the philosophy and empty deception according to human tradition, according to the elementary things of the world and not according to Christ;
(Hebrews 13:9) Do not be led astray by various and strange teachings, for it is better for the heart to be strengthened by undeserved kindness than by foods, which do not benefit those occupied with them.

The Encyclopedia of Religion admits: “Theologians today are in agreement that the Hebrew Bible does not contain a doctrine of the Trinity.” And the New Catholic Encyclopedia also says: “The doctrine of the Holy Trinity is not taught in the O[ld] T[estament].”
Similarly, in his book The Triune God, Jesuit Edmund Fortman admits: “The Old Testament . . . tells us nothing explicitly or by necessary implication of a Triune God who is Father, Son and Holy Spirit. . . . There is no evidence that any sacred writer even suspected the existence of a [Trinity] within the Godhead. . . . Even to see in [the “Old Testament”] suggestions or foreshadowings or ‘veiled signs’ of the trinity of persons, is to go beyond the words and intent of the sacred writers.”

Yes, it's very obvious that Jesus did not exist in the Old Testament. There was a God and Holy Spirit, but no Son.
 Try this, write down the definition of a tricycle, then match it to its definition in a dictionary ("a velocipede with three wheels").
Write down the definition of a tripod, then match it to its definition in a dictionary ("a stool, table, pedestal, etc., with three legs").
Now, let's see if the Father, the Son, the Holy Spirit, can be considered a threesome, as the main characters, when grouped, in the New Testament.

This post was edited by antibiotic at February 17, 2018 5:38 AM MST

Wrong about Jesus not existing in the so-called Old Testament. 
Jack, Janet and Chrissy are on Threes Company but not the same person, same age, same strength etc.
Blood water and spirit are mentioned together in the Bible but they are not the same entity.
Lord, faith and baptism are mentioned together but they are not the same entity.
Paul Silas and Timothy are mentioned together but they are not a trinity.
Larry Mo and Curly?

Now Pagan religions were full of triad gods.
Amon-Ra, Ramses II, and Mut.
Horus, Osiris, Isis
Ishtar, Sin, Shamash,
moon god, Lord of Heavens, sun god


The trinity developed much the same way as the holidays did. Adapting pagan customs and doctrines.

Jesus, son of God, born of the virgin Mary is not mentioned in the Old Testament. Jesus is not Michael. 

Now Pagan religions were full of triad gods.
Amon-Ra, Ramses II, and Mut.
Horus, Osiris, Isis
Ishtar, Sin, Shamash,
moon god, Lord of Heavens, sun god.
All triunes made up by man.

Jack, Janet and Chrissy are on Threes Company but not the same person, same age, same strength etc.
Blood water and spirit are mentioned together in the Bible but they are not the same entity.
Lord, faith and baptism are mentioned together but they are not the same entity.
Paul Silas and Timothy are mentioned together but they are not a trinity.
Larry Mo and Curly?
Yeah, more man made nonsense. 

Don't forget Peter, Paul and Mary.

Do some study on other things which come in threes. 
https://www.nwo.nl/en/research-and-results/research-projects/i/44/27344.html
Parts of small stellar systems created by what you call Jehovah God. Real stuff, no man made nonsense.

Human behavior flows from three main sources: desire, emotion, and knowledge.  – Plato (not from the bible)

Our creator seems to like the number three.
~ There are three main types of stable particles: the proton, the neutron, and the electron. 
~ There are three “generations” of leptons.
~ There are three types of charges: positive charges, negative charges and neutral charges.
~ There are three main properties associated with subatomic particles: mass, charge, and spin. 
~ There are three types of color charge involved in the strong nuclear force: red charges, blue charges, and green charges.
~ There are three dimensions of space: height, width, and depth.
~ There are three main types of matter: gaseous, liquid, and solid.
~ There are three main types of massive objects: planets, stars, and galaxies.
~ There are three main types of galaxies: spiral galaxies, irregular galaxies, and elliptical galaxies. 
~ There are three types of natural laws: the laws of physics, the laws of chemistry, and the laws of biology.

No man made nonsense.

 

The Catholic Church seems to think that Jesus existed before the first century? 
https://catholicexchange.com/the-hidden-story-of-jesus-in-the-old-testament


Back to the Bible, Jesus existed before being born of Mary. God existed before Mary as well.
(John 8:54-58) Jesus answered: “If I glorify myself, my glory is nothing. It is my Father who glorifies me, the one who you say is your God. 55 Yet you have not known him, but I know him. And if I said I do not know him, I would be like you, a liar. But I do know him and am observing his word. 56 Abraham your father rejoiced greatly at the prospect of seeing my day, and he saw it and rejoiced.” 57 Then the Jews said to him: “You are not yet 50 years old, and still you have seen Abraham?” 58 Jesus said to them: “Most truly I say to you, before Abraham came into existence, I have been.”
(Proverbs 8:22) Jehovah produced me as the beginning of his way, The earliest of his achievements of long ago.
(John 17:5) So now, Father, glorify me at your side with the glory that I had alongside you before the world was.
(Philippians 2:6, 7) who, although he was existing in God’s form, gave no consideration to a seizure, namely, that he should be equal to God. 7 No, but he emptied himself and took a slave’s form and became human.
(Colossians 1:15-17) He is the image of the invisible God, the firstborn of all creation; 16 because by means of him all other things were created in the heavens and on the earth, the things visible and the things invisible, whether they are thrones or lordships or governments or authorities. All other things have been created through him and for him. 17 Also, he is before all other things, and by means of him all other things were made to exist,
(Revelation 3:14) “To the angel of the congregation in La·o·di·ceʹa write: These are the things that the Amen says, the faithful and true witness, the beginning of the creation by God:
(Micah 5:2) And you, O Bethʹle·hem Ephʹra·thah, The one too little to be among the thousands of Judah, From you will come out for me the one to be ruler in Israel, Whose origin is from ancient times, from the days of long ago.

The Father is the only true God.

(John 17:1-3) Jesus spoke these things, and raising his eyes to heaven, he said: “Father, the hour has come. Glorify your son so that your son may glorify you, 2 just as you have given him authority over all flesh, so that he may give everlasting life to all those whom you have given to him. 3 This means everlasting life, their coming to know you, the only true God, and the one whom you sent, Jesus Christ.
(1 Corinthians 8:5, 6) For even though there are so-called gods, whether in heaven or on earth, just as there are many “gods” and many “lords,” 6 there is actually to us one God, the Father, from whom all things are and we for him; and there is one Lord, Jesus Christ, through whom all things are and we through him.
(1 Corinthians 11:3) But I want you to know that the head of every man is the Christ; in turn, the head of a woman is the man; in turn, the head of the Christ is God.
(John 14:28) You heard that I said to you, ‘I am going away and I am coming back to you.’ If you loved me, you would rejoice that I am going to the Father, for the Father is greater than I am.

(Galatians 4:14) And though my physical condition was a trial for you, you did not treat me with contempt or disgust; but you received me like an angel of God, like Christ Jesus.

The head bones connected to the neck bone.