How did God come into existence?

I am having trouble understanding how God came into existence. My Catholic school taught me that He never had a beginning and has existed forever and will continue to exist forever.

I have been watching a lot of cool physics and biology videos on youtube and a common theme seems to be that complexity evolves from simplicity. This seems to be true whether you're speaking of life or stars or elements, etc.

It got me to thinking that explaining the universe's origins with God presented a new problem to me. Where did He come from? It does not make sense to me to say that something never had a beginning. Not only is it impossible for me to conceptualize that in my head, it does not make logical sense to me either. Perhaps time is cyclical and that is how things might not have beginnings, but how did the cycle come about?

Does anyone know how God could have originated?