That's one of the ideas of the universe itself. Also, as research into the nature of time continues, this entire subject of beginnings may become moot.
A common answer is that God is infinite and transcendent and therefore needs no creator.That's one of the ideas of the universe itself.
That's exactly my point, from my very first post on this thread. May atheist cosmologists are unable to accept that our finite universe could spring from "nothing". So they posit theories that "attach" some infinite "source" for the universe, like a multiverse---with no supporting evidence for it whatsoever. In effect they demonstrate a measure of irrational faith not unlike what theists have.