Yikes, that sounds frustrating. This will probably not be a one-and-done solution, but there are some steps you can take to figure out what is wrong.
Look for any useful information in event viewer (entries right before/including the critical failure shutdown)
Check S.M.A.R.T. status for your drive (using SSD-Z or other disk utility)
Are you able to run FurMark for 15min without crashing? If not, your GPU may be part of the problem
If you are comfortable with computer hardware, try removing some of the RAM (test with each stick to identify any potential bad stick)
~~Freezing/crashing when loading specific assets could indicate failing storage media. You mentioned that you are crashing at other times as well, but you could still try installing warframe to a different drive, as a fallback.~~ (looks like you already tried this one)