I have (had) the exact same issue after upgrading from Fedora 31 to 32 beta, but with the Intel i915 driver, not noveau.
It happened each time I booted, and half the time my system would hang later after initiating a clean shutdown.
I tried lots of workarounds:
- turn monitor dcd off
- turn dmps off
- forced xorg to xua
- forced xorg to sna
- disconnected 1 of 2 monitors
- forced power mode off for i915 graphics
- turned off all extensions, including dash2panel
- uninstalled gnome-tweaks
But none of this made a difference.
I was using Gnome.
Then on the same pc I added KDE-Plasma, and switched to that DE/WM. After that the system has not shown any crashes or shutdown hangs anymore.
So it seems the issue is caused by the Gnome/Xorg combination.
Hope this help.
Regards, Ids.