The screen locks itself too quickly
If you leave your computer for a few minutes, the screen will automatically lock itself so you have to enter your password to start using it again. This is done for security reasons (so no one can mess with your work if you leave the computer unattended), but it can be annoying if the screen locks itself too quickly.
To wait a longer period before the screen is automatically locked:
Click the icon at the very right of the menu bar and select System Settings.
Click Brightness and Lock.
Change the value in the Lock screen after drop-down list.
If you don't ever want the screen to lock itself automatically, switch Lock off.