I wasn't a born in, I came in at the age of 13, first raised as a catholic so I was used to believing that god existed and took a personal interest in me.
During a JW study I remember reading that motion must come from motion and life from life. So of course the question of where did god come from popped into my head. And based on that question, I realized that when it came to the gods religions had made it up as they went along. I was a little disappointed when I realized that.
I don't think about nothing because I've experienced it....before I was born of course then again during open heart surgery, they were rolling me into the operating room, hit me with a shot, had me count backwards, 99 (they won't be able to put me under, I remember thinking) 98, 97.................................the best thing for humans about nothing is that it's an absence of all external and internal stimulation and totally pain free at least when death finally overtakes us.
The only thing disconcerting about reaching nothing is the potential for first experiencing pain and sorrow.
As far as where god came from ............... Out of the imagination of mankind. Why? Probably because we are the only species that are aware of dying. It's a frightening prospect so people have been speculating on whether or not there is something else on the other side since mankind became aware. You know this concept of one god came rather late to the dance. People looked to thousands of different gods in hopes of finding a better life and ultimately a way out long before the single god concept became the norm for Jews and Christians.