Growing up as a Jehovah’s Witness Christian, I’ve never in my 20+ years of actively studying the Bible, ever found substantial evidence of the Trinity being true. And am I the only one? No.
"Neither the word Trinity, nor the explicit doctrine as such, appears in the New Testament, nor did Jesus and his followers intend to contradict the Shema in the Old Testament: 'Hear, O Israel: The Lord our God is one Lord' (Deut 6:4)" - The New Encyclopedia Britannica (1976, Micropaedia Vol. X, p.126)
We could imagine, if this was shown to a Christian who believed in the Trinity Doctrine, that they would choose to ignore the statement, by using the excuse that it was probably written by someone who wasn’t a Christian, or believed in God. No matter how evident the proof is. So let us read a statement from a Catholic perspective:
"The formulation 'one God in three Persons' was not solidly established, certainly not fully assimilated into Christian life and its profession of faith, prior to the end of the 4th century. But it is precisely this formulation that has first claim to the title the Trinitarian dogma. Among the Apostolic Fathers, there had been nothing even remotely approaching such a mentality or perspective." - New Catholic Encyclopedia (1967, Vol. XIV, p.299)
This explanation is pretty evident – the Trinity Doctrine was never taught by Jesus. It was not ever even close to being suggested as a part of biblical teachings until the 4th Century.