Incosistent boot failure

[Platon]

Hello, this seems to be proper place to ask for advice

I build my computer about half-year ago and now this problem occurred

If I shut down computer and want to start it again in short time, it fails to boot and speaker beeps. Then if I let it sit for a while it starts completely normal, without any intervention.

No other strange behavior just this buggs me, why is it happening - under heavy load or idle no problem, no heat, no artifacts, no nothing, it works fine when it is on.

Suggestion from friend was, that my gigabyte p55m-ud2 may has some problem with bios - I successfully flashed my default version f4 to current f11, but issue remains. So next thing that comes into my mind is probably PSU - but I encountered PSU problems before on more than one system and it always showed when computer was working, or it failed to boot completely.

Would any of you have any suggestion for what should I look for in my "no tools, except screwdriver" conditions? Also I am not sure that boot failure happens always, as my pc goes on for most of the day and to try it on purpose occurred to me only now : ]

I built it myself, so I am capable to disassemble it and look for "something".

here are specs:
cpu - i750 (2.66ghz) + coolermaster hyper 212+
ram - 2x a-data stick 2gb 1333mhz ddr3
mb - gigabyte p55m-ud2
gpu - radeon 5750, don't remember company, maybe gigabyte also
hdd - 500gb samsung
case - coolermaster elite 330
PSU - fortron 500w 80% certified

could it be that some fancy safety measure in PSU kicks in? I do not know what all those nice features are
http://www.alza.sk/fortron-bluestorm-bronze-80plus-d153206.htm
it is in slovak but down in description are these acronyms and I think they are in english

Also I think it is important to emphasize that when ON computers work with no problems.

 

[Griffolion]

I had a similar thing with an old machine of mine. I would turn the computer off, and if i wanted to go straight back on, pressing the on button would make the computer turn on for about half a second and then shut off. Pressing the on button after this would have no effect, i would have to switch the power off at the PSU for 10 seconds and on again. This process could happen a few times before it would actually switch on again. If you waited a good 2 minutes before switch on, it would be guaranteed to turn on fine. I put it down to a heat issue as something as strangely variable as this is generally down to heat of some description.

If you have any spare parts to get hold of, test the system out with another PSU to see if it is something about yours that is odd.

 

[Scott2010au]

When it beeps, how does it beep during the failied boot?

Does it fail to boot, auto-reboot, then auto-reboot again when this happens?

 

[Platon]

thanks for replies

It fails to boot and beeps one long, two short beeps, it does not auto-reboot, as it just beeps, than sit there as a duck until I put it off with power-button.
Also there is no noticeable heat anywhere in sight.

I thought even before that I will have to try another PSU, but I just don't have any powerful enough in supply, so I am trying these "other" things.