However, lately, Avast has been asking to restart my PC at least 1 a day (sometimes two).

What is the exact message or post a screenshot ?

Operating system restart needed by avast message - First check the contents of the C:\Program Files\Alwil Software\Avast4\Setup\setup.log file, which should show you why it thinks the reboot is needed.

This could be solved, in some systems, by deleting the file C:\Program Files\Alwil Software\Avast4\Setup\reboot.txt