I’ve read good things about LTX, but I’ve never used it.

Hangs, reboots or does it turn off? Depending on that it could be a plethora of things.

Do you get any error prompts? Any red alerts when restarting?

Did you check that the monitor works steadily on another system/OS?

Did you try another DE, even on a live usb?

Is the HDD/SSD healthy?

Are all the fans working? Is it the thermal protection?

Is the PSU healthy and or the power connection damaged?

Does your system have a centralized logging like journalctl or can you reach the single log files to check and add more information?

It could literally be anything, even aliens.