From time to time, with no pattern that I can discern, my laptop goes into a mode in which it locks the screen whenever it becomes “idle”. (I have it set to consider itself to be idle after 30 minutes of inactivity.)
This is no big deal; I just have to key in my password and it unlocks. But it is annoying. And mystifying. What could be causing this behaviour? I have taken no overt action to initiate screen locking.
In Control Center -> Screensaver I definitely do not have the box “Lock screen when screensave is active” ticked. And I can find no other allusions to locking the screen amongst the various tools in the “Control Center”.
Can anyone suggest what might be going on and how I might stop it from happening?
Note that rebooting does not seem to help. But then, after some time (with no discernable cause) the screen locking behaviour will cease. And then after some more time (weeks, months) recommense. Weird.
I am running Ubuntu 16.04.2 and Mate 1.12.1.