I’‘ve had enough of this. I have just booted my PC today and this again.
I had everything set on Ask as suggested, but it only asked one question and there wasn’t even an option to take no action. It still quarantined all my files… WTF?!
I did a full scan yesterday, Avast found nothing, just a few wannabe-PUPs which weren’t PUPs (I manually enabled searching for PUPs).
Of course, all chested files’ startup entries have been removed, too.

From what I’ve noticed, it only happens on first boot of the day (?)

I DEMAND EXPLANATION and uninstalled your antivirus. This went too far.

EDIT: removed caps and cursing because I felt bad about it and I know it’s not your fault… I’m still enraged though