The doctrine of the Trinity? Nope.
But a simple belief in Jesus as God was there right at the start of Christianity – it was a triune Church before the close of the first century.
There are two passage in Paul which are now believed to be very early hymns:
The first is Colossians 1 15-20 – "He is the image of the invisible God"
The second is Philippians 2:5-11 – "Have this mind among yourselves, which was in Christ Jesus,"
Notably the latter part of the Philippian hymn (v9-11):
"Therefore God has highly exalted him
and bestowed on him the name which is above every name,
that at the name of Jesus every knee should bow,
in heaven and on earth and under the earth,
and every tongue confess that Jesus Christ is Lord,
to the glory of God the Father."
"The name which is above every name" is telling and, to Jewish-Christian ears, is clearly a reference to the Divinity of Jesus – "That at that name of Jesus every knee should bow" is either an instruction to break the Commandment, or that Jesus is God.
"Jesus Christ is Lord" should also not be passed over. Jews do not pronounce the tetragrammaton (YHWH) in the Hebrew and the accepted Hebrew form of address was 'Adonai' which in Greek is 'Kyrios' – 'Lord'.
The language of the hymns is not characteristically Pauline, and scholars have noted they translate easily back into Aramaic, so may well have been translated from Aramaic to Koine Greek. They certainly show features of Hebrew poetic structure.
They are most likely recognised credal statements in hymnodic form before their incorporation into Paul’s letters. Most scholars date them from 33 to 48 – time enough to become known before Paul was writing, and they evidence a belief in a fully human, fully divine Jesus.
That Christology was not defined until Chalcedon, 400 years later, but was evidently there, and believed, right from the get-go.