The type and version of the OS in question is not specified, but if it was about furmark and cinebench, it Windows.
Go to control Panel -> System -> advanced system settings -> Advanced tab -> startup and recovery
, uncheck the item "automatically restart" and check the box for "write an event to system log". The memory dump can not touch. Then wait for the next reboot.
First, you need to find out whether there will be any BSOD and the error number will be written on it. If not mistaken, the default Win10 output the error number is disconnected. How do I enable it specified, for example, here
. Secondly, after restarting, go to control Panel -> administrative tools -> computer Management -> event Viewer -> Windows logs -> System
and see over time what errors or mistakes happened just before reboot. This will give food for further reflection.