Apart from the controversies throughout church history and even in our day, it is clear that the New Testament writers were settled on the doctrine of the Trinity. That is, they were ok with and even consumed by the One God who eternally exists in Three Persons.
What is amazing about this to me is the way in which they seamlessly swing from the Old Testament of One God with its subtle intimations of specific personhood to the New Testament’s emphatic statements of the God, who is three in one.
BB Warfield is helpful here in his book, The Biblical Doctrine of the Trinity
To their own apprehension they worshipped and proclaimed just the God of Israel; and they laid no less stress than the Old Testament itself upon His unity (John 17.3; 1 Cor. 8.4; 1 Tim. 2.5). They do not, then, place two new gods by the side of Jehovah as alike with him to be served and worshipped; they conceive Jehovah as at once Father, Son, and Spirit. In presenting this one Jehovah as Father, Son, and Spirit, they do not even betray any lurking misgiving they take over Old Testament passages and apply them to Father, Son, and Spirit indifferently.
and further…
If they betray no sense of novelty in so speaking (of God as a Trinity), this is undoubtedly in part because it was no longer a novelty so to speak of Him. It is clear, in other words, that, as we read the New Testament, we are not witnessing the birth of a new conception of God. What we meet within its pages is a firmly established conception of God underlying and giving tone to the entire fabric. It is not in a text here and there that the New Testament bears its testimony to the Trinity. The whole book is Trinitarian to the core; all its teaching is built on the assumption of the Trinity; and its allusions to the Trinity are frequent, cursory, easy and confident….The doctrine of the Trinity does not appear in the New Testament in the making, but as already made.
Due to the centuries of conflict we often overlook the fact that this doctrine was not only settled but delighted in. It is good to be reminded of this and to be ourselves Trinitarian hounds who work through the Scriptures with our noses to the text only to pick up the glorious scent of the Triune glory!