That one comes up a lot as some kind of counter argument, what caused the causer, who caused God? We have no way of defining God, but most minds tend to wander towards some kind of religious imagery of God, which doesn't lead us anywhere and adds nothing to our understanding. There has to be a baseline, an Uncaused from which all cause is generated, otherwise we have a regression of infinite causes and time and the present would not exist.
The system must have an uncaused basis from which all cause flows, otherwise we have a paradox in which along the line of infinity something caused itself before it existed and that is not a possible.
I don't think there is a definitive start and finish to anything, just constant change. Creation, whatever that is has had no beginning and will have no end. I do like Hindu cosmology because it speaks of great cycles in which a universe breaths out and comes into existence then breaths in and starts all over again across trillions of years and this has occurred an infinite number of times.
Who knows, it just seems to me that an agent of Cause is the only answer that seems plausible, seeing as the other options of accidental cause and involuntary cause are not possible. There may be some other option we don't know about?
