At a guess I'd say it may be your CPU temp not your GPU..
Your attached note before shutdown says CPU usage 77%, and you seem to get same result for any version of C4d renderers - standard, physical are all CPU. I suggest install CPU-Z to monitor CPU temp.
I'd check the cooling for your Ryzen 3900, and if it's working correctly- there was a version of 3900 that came without the default cooler, a more powerful liquid cooler was recommended.
Otherwise it would be useful to know what GPU render engine you were using.
Regards
Edit: Sorry not CPU-Z, Real Temp was the one I was thinking of, but whatever does the job for Ryzen.
