On a Flexi PM
computer.... make sure it is not running out of disk space. In
Windows Defender or other antivirus find the advanced settings to exclude the Flexi folders in PM.
Deleting old jobs from PM generally does okay but I've found that Flexi still often leaves behind a lot of files and it takes manually digging through temporary folders to find the stragglers (mostly in various folders under the "Jobs and Settings" folder).
Once in a long while clear the PM job log (top "view menu").
As others mentioned make sure of power settings, screen saver settings as well. I've always had ours to ONLY put the monitor to sleep after a few hours (be aware if you have and use monitor USB pass-through ports).