My PC is shutting down by itself

[Martin_167]

The first time it happend I wasn't really stresing my PC I think i was waching youtube in firefox with another tabs open and some other programs opend but they weren't to many, probably ram gpu and cpu usage weren't higher than 40%, and today I had skype and steam and firefox open and it shut down, even weirder when it shuts down it powers back up automaticly without any problems
Here are my pc specs:
-Gigabyte GA-H61M-S1 (rev. 2.1)
-Core I5 2130 with stock cooler
-Nvidia GeForce GT610 1GB MSI
-Crucial Ballistix Sport 8GB DDR3-1600 UDIMM
-Generic PSU that came with the case 500W

 

[Ralston18]

Open Event Viewer and look for error codes and warning just before or at the time of the shutdowns.

Reference:

http://www.tomshardware.com/faq/id-3128616/windows-event-viewer.html

It takes some effort to get a sense of the logs but no harm in exploring. Sometimes the log may report no entries but it is really pulling them together and eventually will populate within a few minutes.

Right clicking any given log entry will present more information.

See what you can fnd.