My 2018 Mac Mini keeps freezing, crashing, and rebooting

It's done this 3 times in the past 3 days.

I'm not sure what I can do about it.

I'm using a 2018 Mac Mini. I'm running from an external usb-c hard drive, due to limited internal space and Migration Assistant failures last year.

I have sensory and coordination issues. I can't use Safe Mode, since it's incompatible with some of my accessibility tools, and I get sick from the diagnostics/repair partition, since it's full of animation.

I am using Mojave due to software compatibility issues.