I HATE CARS!!!!(not starting)

So A couple of days ago I was at work sitting in mycar, when I wanted to start it, It wouldn't. I towed it home and the next morning it started. Later I went to take it over to the local autozone to do a diagnostics test on it and it wouldn/t start. I took off the starter and took it to the local autozone and they tested it and it was fine. But it just didn't make sense to me so Ididn't buy it. there was no sound like the selenoid was going out. Can anyone help Me !?!?!?!?!?! Please I need help!
thanks in advance.
95 g20
auto
126,000 miles

I think I'm having a similar problem. I've got a '96 P10. The other day it wouldn't start after a routine 20 minute trip. When AAA got there the car started right away. So I took it to my mechanic and the car tested completely fine. A week later, I was driving to work, then I heard a pop through the radio. I turned the radio off, but I could hear a whine through the speakers that went up and down with engine rpm. The motor then cut off five minutes later. Afterwards, I turned the key and it started right up.

My mechanic thinks it's the alternator going bad, but he's reccommending that I wait until it fails, since these things can be tricky.