All your experiences come from living in a nice cozy little world with moderate gravity moderate speeds, temperatures etc. etc.
When you get outside these boundries you find that things like time don't work the way you think they do.
Time is intrinsically linked to space when you start talking about the begining of space you also mean the begining of time.
Your language starts to break down - words like begining, before, start, end don't really have any meaning anymore.
Having said that nobody is quite sure whether our universe will "end" or not, currently the smart money is on it being 'open' that is that it will continue "forever".
But there are a few big unknowns in particular the nature of something called dark energy which seems to be accelerating the Universe's rate of expansion and we really need to understand that first.