1]
avast doesn't scan randomly
2]
If the scan increases the boot time with 2-3 minutes, you have a slow system and/or many things loading at boot-time (likely several that are not needed).
3]
xampp is meant to be run on/as a server (software).
Meaning there is no need to (re)boot a system unless there is a update (hardware/software) for the server
1) ok
2) yeah well my system could be the slowest in the world, but procmon doesn't lie. Sure, Avast likes massively scanning windows stuff like "windows\assembly\NativeImages", "system32\CatRoot", Nvidia stuff but also a number of other user applications like OpenOffice, MikTex, LyX, GIMP, steam... over and over at every startup since weeks. I think i made the situation more bearable by disabling windows prefetching/superfetching and windows updates but only to a extent. I see sometimes the "instup" process firing, which would mean avast updating its definitions during that mayem which would not help.
When i feel like i will try to temporarily uninstall avast and re-enabling defender and see if the situation changes.
3) cool story, bro