A miner work is never easy... seems to be easy, but only when doing it you realize how much work is needed...
have you been able to see what shows on the screen just before freezing? Any error? Any GPU with odd values?
In my experience this kind of problem is usually caused by riser cables (that need to be tested one by one).... riser cables are mostly to blame for everything that happens on your rig
or maybe you did some kind of excessive overclock?
in the end, you can also try to switch the RAM from the good to the bad, or try the PSU as other user suggested...
Also double check your OS settings, especially if Win10. Is powersaving on? Increase virtual memory, turn off updates, check Defender is not causing trouble.
But to be honest the list of things is huge - could be an internet issue, wifi?, could be OS, could be risers/psu or overclock. Might be RAM or something more annoying, but usually it's OS/clocks as peeps have said.