Had a bit of a scare the yesterday. Was going to install a new hard drive, which I figured was simple enough. Plugged it in and turned on the computer. The computer turned on... for a about a second... then turned itself off. Tried turning it on again but nothing at all happened. Completely dead. I tried switching on and off the PSU, replugging the power cable, still nothing. Tried unplugging the hard drive I just installed, still nothing. Unplugged all hard and dvd drives and then it turned on. Plugged in my main hard drive, still good, the new drive, still good, dvd drives, still good. So basically I had now booted up the exact same setup as when it refused to turn on.
I'm definitely not expecting anyone to know why my computer didn't want to turn on in my particular case, but I'm just really curious: What are common/possible reasons for a thing like this happening? What throws me off is the fact that it is working completely fine now. If the PSU or the mother board or something had actually died I could've understood it. It doesn't work, so it doesn't turn on.
But how can it refuse to turn on just for a short moment of time? Did it just feel like taking a break? Did my replugging of components change anything? What are reasons for something like this happening?