First thing with an issue like this is to check temperatures, most PC's will shut themselves off to avoid damage if they get too hot and this game is fairly poorly optimised and can give graphics cards a hard time. CPUID Hardware Monitor has a free version to use. 

If its not that then I would suggest seeing if its a crash, older versions of windows had an option that was normally automatically checked to restart the pc on Blue Screen crashes, not 100% sure if Win 10 has it but it would be worth checking out as it could yield information as to the cause.

After that you need to start looking at Power Supply and RAM as both of these could cause the issue as well, there are several free programs to test RAM.