Hello!
Two days ago I encountered this issue at my computer’s startup when Avast free seemed to start a little slower than usuall. First when it started, it showed up with program icon with little red cross and telling “Avast backround service is not running”, but after a while it changed to green and started working normally. This happened over a couple of test reboots and I tried Avast repair with no effect. I failed to find any threats with neither Avast or Malwarebytes. But as of last evening and this morning, the problem seems to have fixed itself, since Avast starts normally again without “You are unprotected!” popup and little program icon in Windows taskbar starting to spin normally as soon as it shows up.
Not only that, but my Avast even seems to work much faster now. Quick scan now takes merely half of time it took a day ago, and full scan only took one and a half hours where before it almost took full two hours.
As I said, the problem itself seems to be gone, but I’m still curious about what might have caused that.