Some changes (bugfixes, UI changes) to Avast are now being announced by the screenshot you posted above.
I don't recall such a run of restarts prior to the current spate of notices, so this is something new, I think, for all of us.
Problem is, information as to the whyfor and reason for the required restart doesn't seem to be present.
I suggest looking in the About section to note/record the program version and UI version before you reboot. Afterwards, check there again to see if anything changed, and if so, what it was that changed. It's likely any changes noted there are the reason for the restart.
NOTE: A recent restart notice turned out to be a fix for the BankMode not starting issue. That fix was deployed by Avast program version 19.8.293 (build 19.8.4793.539).
Current build number is now 19.8.4793.541, and that one did require a reboot to take effect.
See attached below: