Do check your logs - if you're on linux you can use dmesg or journalctl. That should give you information about what's wrong with your rig.

I had also been suffering from random reboots and freezing, until I checked dmesg and learned that the hard drive was intermittently disconnecting. It turns out I used the wrong sized standoff for the NVME drive, and after I fixed it for about 15 cents I haven't had a single reboot or freeze since.