All right, your question, “Where did God come from?” assumes that you’re thinking of the wrong, obviously displays that you’re thinking of the wrong God. Because the God of the Bible is not affected by time, space or matter. If He’s affected by time, space or matter, He’s not God.
Time, space and matter is what we call a continuum. All of them have to come into existence at the same instant. Because if there were matter but no space, where would you put it? If there were matter and space but no time, when would you put it? You cannot have time, space or matter independently. They have to come into existence simultaneously.
The Bible answers that in 10 words. “In the beginning”, there’s time, “God created the heaven”, there’s space, “and the earth”, there’s matter. So you have time, space, matter created, a trinity of trinities there. Time is past, present, future, space has length, width, height, matter has solid, liquid, gas. You have a trinity of trinities created instantaneously, and the God who created them has to be outside of them. If He’s limited by time, He’s not God.
The god that created this computer is not in the computer, he’s not running around in there changing the numbers on the screen, OK? The God Who created this universe is outside of the universe. He’s above it, beyond it, in it, through it, He’s unaffected by it. So the concept of a spiritual force cannot have any effect on a material body, well then I guess you have to explain to me things like emotions and love, and hatred and envy, and jealously and rationality. I mean if your brain is just a random collection of chemicals that formed by chance over billions of years, how on earth can you trust your own reasoning processes and the thoughts that you think?
So your question, “Where did God come from?” is assuming a limited God. And that’s your problem. The God that I worship is not limited by time, space or matter. If I could fit the infinite God in my 3 pound brain, He would not be worth worshiping, that’s for certain. So that’s the God that I worship, thank you.