People get caught up in how the universe came to be, since once you fix a starting point, it is relatively easy to go forward. But the starting point always nags at us. So, it is easy to get a shirt if you start with a thread. Just weave it. But where does the thread come from? It comes from cotton. Where does cotton come from? Well it grows from plants. And so on goes the line of reasoning each system emerging from something else. My claim is that every system has this infinite regress property that cannot be resolved. Even mathematics has this problem and has to "pull itself by its bootstraps." Set theory constructs all of mathematics by starting with literally nothing — the null set — which is defined to be zero. The set that contains a single element — the null set — becomes the number 1, the set that contains two elements — the null set and the set containing the null set — becomes the number 2, and so on.
The concept of zero in number theory took a while to be thought of and accepted. Perhaps my old memory has betrayed me again. Too old to be inclined to search.
If anybody hasn't read it already, I strongly recommend the book A Universe from Nothing by Lawrence Krauss
Not dissimilar from a Mandelbrot set or y = 1/x -> 0 as X gets larger. There is no starting/stopping point. Just very close to zero.