When i leave the pc running a full scan ,when i return the pc has ben shut down after he scan has been completed, is thee a setting i can adjust to stop this at all?
The default action is NOT to shutdown after a scan - so that must have been changed.
You don’t say what version you have - the latest being 9.0.2021:
Open the Scan settings for the scan that you are running > Scheduling - uncheck the ‘Shut down the system after the scan finishes’ option.
It can also be a windows or bios setting that causes it to shutdown.
Or a lack of routine system maintenance. Excessive heat production can be an issue. Ever clean it? Know how?