That is a question to which there is no answer yet, and may never be. You're basically asking what space and time are, and while plenty of models and theories OF spacetime exist, "what came before" is really the realm of philosophy and religion barring major breakthroughs in an understanding of quantum gravity, and probably a lot more.
That said, this doesn't stop theories to explain what you're saying from being proposed. There is something called Brane Cosmology (purely theoretical) as part of String/M-Theory which you might enjoy a bit of reading into. In that formulation, we're confined to dimensional "memBranes" in a multiverse of membranes. Fluctuations lead to sporadic collisions between branes, and the at that contact point what we call a universe is created. Truly, very elegant, totally untestable, and not substantially different from a wild guess.
Physics can bring you CLOSE to those answers, and better yet, it gives you REAL guidance away from crackpottery et al. For answers to "why" or the ultimate, "from where" it's hard to imagine a scientific answer in our lifetimes, but we can dream.