The mystery is the three is one, the one is three.
The Nicene Creed
We believe in one God, the Father Almighty, Maker of heaven and earth, and of all things visible and invisible.
And in one Lord Jesus Christ, the only-begotten Son of God, begotten of the Father before all worlds (æons), Light of Light, very God of very God, begotten, not made, being of one substance with the Father; by whom all things were made; who for us men, and for our salvation, came down from heaven, and was incarnate by the Holy Ghost and of the Virgin Mary, and was made man; he was crucified for us under Pontius Pilate, and suffered, and was buried, and the third day he rose again, according to the Scriptures, and ascended into heaven, and sitteth on the right hand of the Father; from thence he shall come again, with glory, to judge the quick and the dead. ; whose kingdom shall have no end.
And in the Holy Ghost, the Lord and Giver of life, who proceedeth from the Father, who with the Father and the Son together is worshiped and glorified, who spake by the prophets.
In one holy catholic and apostolic Church; we acknowledge one baptism for the remission of sins; we look for the resurrection of the dead, and the life of the world to come. Amen.
Its not so complicated. Quit looking for the mechanism: G*d is the alpha and the omega. He's always been, he will always be: he is the great I AM. We don't need to understand the mechanism, its not important - what is important is He is here for us.