Most likely you have a hardware or driver issue. MS tier 2 support pointed to hardware on mine. The only major components I hadn't replaced were the MB and the CPU. But having replaced those now I still get black screen and GPU shutdown occasionally.
Trouble is, getting a lot of crashes can corrupt the OS files and force a reset or worse. And pinpointing the cause can be very complex. If I had it to do over again I would but the OS on its own drive so i wouldn't need to reinstall all the apps after it goes south. Still a pain though.