One cannot state that question without also asking "where did God come from?". Any answer applicable to one is equally applicable to the other, and no answer I can think of is particularly satisfying to either.
There is no logical problem with assuming indefinite existense of either God or existense. (I have intentionally avoided using the expression "material existense" as I believe that it is a subset of existense itself, which may or may not include a "supernatural" [non-material] existense.)
Since positing either that God always exists or the universe always exists leads to no logical contradiction, and either other premise that requires a "beginning" is either self-contradictory or requires a further supposition (of whatever preceded the hyopothetical beginning), one or the other must always exist, God or existense-without-God.
If you are a thorough-going naturalist, the answer is the univers always exists (in some form). If you are not convinced of the naturalist position, you better consider God.
(There is an intentional flaw in this argument. Do you see it?)
Hank