God is not limited by the time and space which He created.
God is eternal which is difficult for a finite mind like ours to totally comprehend.
God is beyond our understanding. If we could understand God fully then we would probably consider ourselves greater than Him, and that is just not possible.
So we cannot completely answer the question of who made God except to say He is Self-existent.
There has never been a time when God did not exist and there will never be a time when God will cease to exist. God is eternal.
17Now to the King eternal, immortal, invisible, the only God, are honour and glory for ever and ever. Amen.
1 Timothy 1:17 (NIV)