Seems to be a power issue or overheating issue, in my opinion. Have you ran benchmarks to stress test your CPU? Download [url=https://www.microsoft.com/en-us/p/cinebench/9pgzkjc81q7j?activetab=pivot:overviewtab]Cinebench R23[/url] and [url=https://www.cpuid.com/softwares/hwmonitor.html]HWMonitor[/url] and run the Cinebench test while having HWMonitor running. If the test crashes your PC, come back here and let us know how the CPU temps were looking like. If the test passes successfully, we can discount a voltage/temperature issue, in my opinion. I was having a similar crash a while ago and it was because I was using custom SATA cables for my GPU, which had deteriorated, and after swapping them out, things fixed themselves. Just my two cents, but that's what I would do to diagnose what is going on, at least from the start. Separate note: your PSU should definitely be enough to drive your hardware, but out of curiosity, what model are you using? Is this a new setup or have you been using this for ages? Inconsistent power and lower-quality PSUs have been the culprit for issues like these for me 99% of the time.

A total computer restart means something truly serious is going on, mostly Hardware-wise.

check your CPU temps when running Destiny , usually PC restart means something is overheating . Download core temp