The universe has always existed and it always will. It has no beginning or end.
This is a philosophical debate. Describing something as having no beginning and no end is a concept that 3-dimensional perspective cannot really understand. I think this is why it is so hard for us (people) to imagine a universe with no beginning and no end. It doesn't work on a Cartesian plane. You cannot 'picture' a 3-dimensional object in this way because there is always a beginning and an end to our perspective. Higher dimensions would better describe an infinite system. Unfortunately, our concept of reality doesn't include any dimensions higher than 3rd. That is why this debate of god, the universe, and infinite existence will always be that, a debate.
I prefer to think of it like this:
Without a shadow of doubt, I know that I am here, now. I can't say that I remember when "I" came into existence, but I do know that "I" exist - at least to me, that is true. This perspective is what makes each and every conscious being a narcissist - unavoidable narcissism.
NOTE: The modern definition of narcissism has become something of an evil. Traditionally, however, narcissism simply means a love of oneself.