iMac will not restart cleanly
iMac, mid 2011, 2.5 Ghz, running 10.13.6
The mac will not restart cleanly. When I reboot, from command line, from the menus, from any way I can imagine, the apps shut down, the screen goes black and I am left with a cursor on the black screen and it never restarts. I have tried a pram, svram, and whatever thing I can imagine and it still is the same. I have a security update that will not apply due to this inability also. I am force to hard power off the mac, and restart with the power button. Then, things work for awhile.
Any help is appreciated. I also have a weird wifi issue that I will post as different question. (Could they be related?)