Hello!
I think, I resolve the problem.
First I checked too memory, PSU, HDD, VGA components, upgrade the BIOS, etc., but problem not resolved.
How I to resolve problem?
When PC has switched off, I remove power cable from PSU, then I remove CMOS battery, then many times pressed power button, after approximaly 30 - 60 sec. I put back CMOS battery, connect power cable with PSU and switch PC on. When PC starting first starts BIOS, after appeared table (between BIOS startup and OS starting). Then was 5 profile:
Profile 1 - Default;
Profile 2 - Last good ... (I don't remember)
Profile 3 - 2 times
Profile 4 - 3-5 times (I think)
Profile 5 - 7 times (I don't remember too)
I think, I have profile 2 active, but I choose profile 1 - default, and pc to start working normally. Now PC starting normally, now PC switched off himself (normally), now start working reset button, before not working. Now I haven't this problem, if you have this problem to try my recipe!
P.S. Sorry my knowledge of English not perfect, but I think here can all understand!