"In the beginning God created the heavens and the earth." The Bible starts with a profound statement, but how else could it begin? If anything exists, something (or someone) must have always existed. In the natural world, something does not come from nothing. The material universe does not appear to be eternal. It seems to be expanding from some point of origin, and it seems to be subject to decay (which indicates an end to everything at some point in the future). For the natural universe to exist at all appears to call for a supernatural origin. This fits well with the first verse of the Bible.
So where did God come from? How long has he existed? How could I possibly understand any answer to those questions? Those are natural questions with supernatural answers. Unless God created himself (and that would be the ultimate paradox), he must have always existed. If so, the concept of time is nearly irrelevant to God. I could ask God, "What were you doing 10 trillion years ago? 100 trillion years ago? 10 billion trillion years ago?" But I could never come to a time when he would not have existed.
Furthermore, when I have been with God 10 billion trillion years, I will still not be close to his age. He will continue to be infinately older than I am.
In so many ways, Genesis 1:1 is humbling to me. I see God as so far above me that words cannot be found to describe the expanse. As the song states, "I stand to praise you, but I fall to my knees."