Problem with black screen after inactivity

[tkn]

could it be like this ?

Desktop environment disappears after login

Sounds like a slightly malfunctioning lid-switch: (monitor open but switch doesn't detect it and puts the laptop in 'sleep' as soon as you login) try this setting: controlcenter->powermanagement->when laptop lid is closed: Do Nothing (both for 'on ac' and 'on battery) If the problem does not appear anymore, it is a faulty lid-switch. (a hardware problem that can be solved by repairing/replacing the switch)