Hello, I think I have finally detected the reason of such behaviour. It was DELL ... and ... me... I have noted that blanked machine wakes up to password prompt when I approach my desk, so looked like a proximity sensing. I do not remember when Dell optimizer has been set up and it had Proximity Sensor enabled! With option to lock and turn off after 60 secs and Wake on Approach. When I disabled this feature all bad behaviour is gone. Seems to me Windows and Dell take too much care about security like modern cars where driver is more passenger then person in charge... Hope this can help others in the future. For me it is too much fighting system with overloaded 'helpers'. Leaving away to Linux, life is easier there and I am the user and not a guest in the Precision environment. Best wishes, Jerzy  
Whatever I change in power settings the machine switches off the screen and always asks for password to come back to work. Switching off Windows Hello does not help at all. This starts to be annoying on new machine with new(?) system.. Please advice... Jerzy
Precision 3561 power management - Windows 11 problem