Using the latest version of Avast Free . . . The computer has to be in Sleep Mode for Scheduling to work (paths below).
The only option is to Shut Down after the scan . . . Is there a way that it could be put back into Sleep Mode?
Full system scan / Settings / Scheduling / [check] Schedule this scan
Full system scan / Settings / Scheduling / [check] Wake up the system to start the scan (if in sleep mode)
Full system scan / Settings / Scheduling / [check] Shut down the system after the scan finishes
Quick scan / Settings / Scheduling / [check] Schedule this scan
Quick scan / Settings / Scheduling / [check] Wake up the system to start the scan (if in sleep mode)
Quick scan / Settings / Scheduling / [check] Shut down the system after the scan finishes