No solution is needed. This is normal and expected behaviour.

Your spinning avast icon in the system tray area is caused by real-time scanning. Avast is scanning files and processes as they are opened and run on your system.
https://en.wikipedia.org/wiki/Antivirus_software#Real-time_protection

This is not the same as you starting a full system scan after which you can view how many files were scanned, how many folders were scanned, and how long the scan took to complete.

It is not recommended to disable or turn off real-time scanning as this is your first-line defence against malware or virus infections. Scans you start such as Quick scan or Full Scan are your secondary line of defence. They won’t help to prevent infections from happening in the first place, as your real-time scanning will. Manual scans are always used to clean up the mess afterwards.