As the title says, my motherboard won't boot up but randomly boots up by itself!
Now a detailed explanation.
Firstly my motherboard is Asus P5GC-MX/1333. When I first got it, I had a 20-Pin PSU of 300W and I've used it for about 2 weeks. Then one day, when I came home I wanted to use my PC as always but this time it wouldn't boot up! I didn't know what to do, I opened my CPU and started staring at it, hoping to find a solution when suddenly, the motherboard boots up all by itself! It didn't load the BIOS though and it wouldn't even turn off so I had to turn off the power switch directly. Then I turned on the main switch and tried booting up the board again but it wouldn't boot up once again and after a while booted up by itself(BIOS not loaded once again). After a number of tries it finally booted up and loaded the BIOS normally and I was able to use the PC.
As the PC finally booted up normally, I took the chance to read the manual of the board in which I found that if a 20-pin PSU is used, a minimum of 350W is recommended! So the next day I bought a 20+4PIN PSU of 500W and connected everything. Back then, everything was working normally, motherboard booting up with BIOS loaded. The following day, I faced the same problem again and even today, before I could come online I faced the problem!
Now one thing is clear, the problem is not about the PSU cause its new and I feel is delivering enough power to the motherboard. Is it the motherboard, ram or something else like capacitors?