PC sometimes shut down itself after waking up from sleep

Hi,

PCPartPicker part list / Price breakdown by merchant

*RAM is 1 set of 3x2GB and 1 set of 3x4GB, so totally 18GB but somehow in OS it only shows 12GB as usable?

*The PSU is actually a 700W but I cannot find it in the part list so...

Usually I put it into sleep before going to bed, in the morning, I wake it up again but after just normal web browsing or maybe just login to my game, it will shutdown\restart itself OR sometimes the monitor will say "no signal" and I have to push the reset button myself.

Sometimes, after even that restart, it can still happen again, but if the issue does not appear, I can run the FurMark stability test as long as I can without any issue and everything is just normal, from web browsing to gaming. BUT during the day, it can still happen just that I notice almost 100% it can happen after a long sleep.

I guess the Video card is not the problem? I am thinking it is because of the PSU? It is well over 4 years old now.

Can anyone help me?

EDIT1: I just check the Windows event viewer and found this error: http://imgur.com/TaG8KTq

EDIT2: Ok so I just encountered the issue again. I was playing CS:GO then suddenly BSOD but since it's Windows 10, there was simply a message saying it's collecting data and will restart soon (1st). However, it didn't restart and just stuck there so I decided to hit the reset button, this time it can go into Windows, then I tried to check the Event viewer to see then it shutdown and reboot again (2nd). But during the boot up, even before the Windows splash screen, it reboot (3rd). Now the third time, it can go in Windows and I'm typing this :( 3 reboots in a very short period. I guess I will run another FurMark stress test to see...