I apologize, but rebooting into safe mode is a rather inconvenient way to get around this problem, and shouldn't be listed as a solution.
A solution denotes that the action performed will resolve the problem permanently, preventing it from happening again. Rebooting into safe mode each time this happens is a workaround, because it doesn't prevent this from happening again. It only allows Windows 10 to perform whatever critical action Avast is preventing during the previous normal boot.
The fact that this happens to begin with notes an incompatibility between Windows 10, and Avast.