Einstein once famously asked this question. Although he was not a "believer" in the theistic sense, Einstein was fond of formulating questions about the universe in guise of what would god do if the universe had been created by an intelligence. It was merely a ploy used to explore some of the deepest questions of physics.
The question does raise an interesting set of additional questions. If god is timeless, at least before the creation of the universe, then it must have been the case that all of god's decisions, thoughts and knowledge, existed simultaneously in a timeless state. So how is it then possible for god to have
willed the universe into existence? How could god, exercising his free will, go from a point of indecision - to decision - on whether or not to create a universe, as well as what kind of universe to create? If god is timeless he cannot have had such a transition, because that would require time.