My computer turns off randomly

My computer randomly turns off. I was trying to upload a video on to youtube when it started shutting down on me. It has since happened to me when ever I try to play minecraft or just upload in general. Its a quick shutdown. I can be on skype for 10 minutes or 4 hours and it will just randomly shut down. It seems that when ever I am going to start something new it tends to happen more often. So the computer screen just go black and everything turns off. I can then immediately turn it back on so I don't think its the computer over heating. I get 40-50 Degrees Celcius at most I am not sure if its the power supply or the motherboard. I just made my computer 3 months ago so its not even old. It always worked perfectly until the last 2 days where it just turns off randomly when I try to use simple programs. I checked if it was a virus with Microsoft essentials and there was nothing.
There are certain points that I just turn on the computer and also just turns off right after. And at other points when the computer just freezes and I can't do anything. I'm guessing to check if its the PSU I must buy a cable to see if its working properly?

My computer specs are as follow:
AMD FX-8350 Processor
Gigabyte GA-970A-D3 Motherboard:
EVGA GTX 650Ti Boost Graphics Card:
8GB Corsair Vengeance DDR3 Memory:
120GB Samsung 840 Series SSD:
1TB Western Digital Caviar Green Hard Drive:
500W Corsair CX500 Power Supply:
Corsair Carbide 200R Case:
OS - Windows 7 System Builder: Optical Drive - Lite-On DVD Burner:
Wi-Fi Adapter - Asus PCE-N15:

Any help would be really helpful as this is stressing me out

 

If it is late at night, it is telling you that it is time to go to bed. If meal time, probably significant other flipping the switch.

Really only way to tell you, is to have you upload some temp readings of what is going on, and any error logs.

 

But there is no error logs at all. It just turns off completely.

 

Computers do not turn off randomly, without throwing errors, or show high temps. Suggest using something like Core Temp, to log the temps and post that info on here. Also download Speccy and post the output from that.

Like I stated, machines do not just shut down, unless it is human intervention, or a system problem. Only other thing, would be just bad power coming into the structure that you are using it in. You would need something like the Ted5000 to monitor voltage for finding out those errors.

 

A "good" UPS with AVR will come with monitoring software that can provide that information too. And, of course, if using a "good" UPS with AVR, and if the shutdowns are being caused by power problems, the UPS would prevent the computer from crashing - which can result in a corrupt boot drive and lost data.

I also agree that computer's don't shut off "randomly". It just appears that way because we (humans) don't see an apparent cause or pattern to the shutdowns. However, unexpected shutdowns can be related to reasons other than heat, and often happen without any error messages.

40-50°C is well within the "good" or safe range, but that is likely for the CPU. Overheating "System" (chipset), graphics, or other components can cause shutdowns too. So you must ensure you have good cooling through the case - the case's responsibility.

Cable? Don't know what cable you would be talking about. The best way for users to test a PSU is to swap in a known good one. PSU testers and multimeters are NOT conclusive because they don't provide a variety of "proper" loads. And testers and most multimeters don't test for ripple (AC noise on the DC) either.

You should probably test your RAM too. You can test RAM using one of the following programs. Both require you to create and boot to a bootable floppy disk or CD to run the diagnostics. Allow the diagnostics to run for several passes or even overnight. You should have no reported errors.

Windows Memory Diagnostic - see the easy to follow instructions under Quick Start Information,
or
MemTest86+ (for more advanced users) - an excellent how-to guide is available here,
or
Windows 7 and Windows 8 users can use the built in Windows Memory Diagnostics Tool. Vista users can test with Vista's Memory Diagnostics ​

Note, however, that software based RAM diagnostic tools are good, but not conclusive. So you might try running with just a single RAM module to see if it fails. Repeat process with remaining modules, hopefully identifying the bad stick through a process of elimination.