As humans we live in a system or universe of time which has the attributes of cause and effect. Nothing happens without something causing it to happen.
Eternity is a whole different dimension, eternity has no time attached to it. There is no time in eternity. No beginning and no end therefore no time. To have a beginning automatically equates to having time.
God created the universe in the beginning, or rather when God started to create “things” outside himself time came into existence.
Is there time in heaven? For God who lives outside time, no. Heaven where angels dwell, there is a perception of time for them. The angels experience time because they had a beginning, once brought into existence angels perceive a sense of time.
“And when he [Jesus] was come to the other side into the country of the Gergesenes, there met him two possessed with devils, coming out of the tombs, exceeding fierce, so that no man might pass by that way. And, behold, they [the devils] cried out, saying, What have we to do with you, Jesus, you Son of God? are you come here to torment us before the time?” Matthew 8:28-29
So we see that devils (who are fallen angels) have a sense of time and the marking off of time sequences.
God being in another dimension without time is something our minds cannot grasp and probably never will be able to grasp. Those in the 1st resurrection who are changed from mortals to immortals, maybe they will be allowed to grasp the concept of eternity but for us other humans who do not get that gift of immortality in the 1st resurrection we will never be able to grasp eternity with our finite minds.
Who created God? No one, God is and that is the explanation he gives, he is and he just expects us to have faith in that statement and he rewards us accordingly….
“But without faith it is impossible to please him: for he that comes to God must believe that he is, and that he is a rewarder of them that diligently seek him.” Hebrews 11:6
God does not try and give us details of his existence and his existence in the dimension of eternity. How could he do otherwise in a way finite minds would understand anyway? he tells us what we need to know. How to worship and serve him in faith according to how he wants us to behave toward him and leaves it at that. What he had man transcribe in the book we call the bible that is all we need to know to please him. All that is recorded in scripture is what he wanted us to know, anything outside of what is in scripture is speculation. We humans are really good at speculating to the point our speculations become our doctrines sometimes.
So my answer to Who Created God? No one. I was taught growing up don’t worry or be concerned about things I can’t control, only be concerned over the things I can control. The same principle applies with God and eternity, don’t burn out my brain thinking about concepts that are beyond my understanding or comprehension, fix my brain on the concepts I can understand and apply to my life.