Having recently upgraded my system I kept finding that my computer would unexpectedly restart, games would crash out and after playing almost any game for 15-30 minutes I would get a Red Screen along with buzzing and then the computer would restart.
As with any issue the route cause and resolution might be different for you but I found that disabling XMP (Extreme Memory Profiles) completely resolved my issues. XMP clocks upthe memory in your system, sometimes above what the manufacturer recommend so this would be classed as overclocking.
Other troubleshooting steps that you could perform if this does not resolve your issue
Check to see if any other components in your system are overclocked (CPU, GPU or Memory).
Check your system and component temperatures and ensure that all fans are running correctly.
Test your Hard Disk Drive using manufacturers or third party diagnostics software.
Test your Memory using manufacturers or third party diagnostics software.
Update the system BIOS
Update drivers (especially Chipset and GPU)