Thanks for the comments, options tried:
Changed UAC to Never, no change.
regedit.exe also requires a password and Cancel on that window doesn’t work so I had to reboot (Cancel OK on Task Manager).
No password required in Safe Mode so does this suggest that some driver, etc is responsible and is there any way to narrow down the problem?
Created a new Admin account which has the same problem.
Ctrl Alt Delete is the normal way I get to window and then the Start Task Manager button. Cntr Shift Esc also takes me to the password screen.
I haven’t tried a earlier restore point but will if there is no other solution. On 12/2 there was a Critical Windows Update, however I’m not sure when the password problem started.
I agree that lack of a logon password is not the best practice but that at least seemed to eliminate the user password as part of the problem.