If God was created, then He is not God.
The eternal God definitively cannot have a beginning. God, a spiritual being, created all material things… all matter, all molecules, all atoms, all things.
If some greater Creative Agent caused God, then that Creative Agent would be God.
“It is reasonable to ask who or what created the universe, but if the answer is God, then the question has merely been deflected to that of who created God. In this view it is accepted that some entity exists that needs no creator, and that entity is called God. This is known as the first-cause argument for the existence of God.” ~Stephen Hawking and Leonard Mlodinow in The Grand Design, page 172
Something cannot come from nothing.
Anything that has a beginning must have a cause.
The material universe has a beginning, therefore everything in the material universe must necessarily have a cause.
It is reasonable to ask where the matter in the universe came from because matter had a beginning. The universe came into existence from something. It is reasonable to expect that a non-material agent from outside the material universe should be the cause of the universe. It is not reasonable to expect that the non-material eternally existent Cause from outside the universe should have a beginning like the things that He created.
God is not a created thing. God by definition is an eternal uncreated being without a beginning. God always was and always will be. He did not create Himself. He doesn’t need to come into existence. God exists without any need for a material source.
Therefore, the original question “who created God” turns into nonsense. It is in the same self-contradictory genre as “Can God make a rock so heavy that even He cannot lift it.” God does not perform nonsensically.
In my view, the existence of this limited universe makes no sense without the existence of the immeasurable transcendent Creator of the universe.