I have a GeForce GTX 750 Ti in my system at work, using the
rpmfusion nvidia drivers (because nouveau can't go more than
a few hours without crashing). Every so often, when the X
server starts or is restarted by logging out, the screen will
go blank and the system will be frozen, needing a power
cycle to get it back.

This only happens at work, a very similar system at home with
a newer model nvidia card never has this problem (though it
certainly had the same crashes under nouveau).

Just curious if anyone else with the 750 Ti has seen similar
symptoms.

NVIDIA GPU GeForce GT 610. I get most consistency using the NVIDIA drivers.  Currently using version 390.77.

DKMS didn't work with the 4.19.7-300.fc29.x86_64 kernel but the manual install did.