Energy must be existing eternally as it can neither be created or destroyed.
Jan if energy as you claim "can't be created nor desroyed", then there's no god. (God can't create energy nor destroy it by your assumption here!.) This small observation would make god, un-omnipotent, not all powerfull since he can't create energy nor destroy it.
If matter came into existence at the time of the big-bang, there must have been previous energy.
Hense the oscillating universe theory. which is under debate constantly.
one version of this theory
There are many other, plus the refutation for such theories as well.
There's no argument however, we've got proof that the big-bang did happen,
though some stuborn theist theologians with there "pseudo" science refute the big-bang theory.
Big Bang theory
And then there's the constant universe theory, of which is self explanatory, the universe has always existed. No big bang, no oscillation, just plain existed.
Constant universe theory
Now out of all three, the one that has been observed, due to the known expanding universe is the big-bang. The oscillating universe theory is the new "kid on the block" in universe theorem, one of which I my self adhire too. The oscillating universe has the big-bang, then after billions of years, when entropy runs it's course the one weakest power of the universe "gravity" beggins to pull back called the "big crunch" hence everything contracts to one finite point then explode again.
Of which ever scientific theory you may choose to believe, though there's no proof, or emperical evidence that a god created the universe, because any entity in existence would have to follow the laws of "metaphisics" and the way that god is described on all religious text of anciet past, contradict the laws of metaphisics.
Godless.