Home Internet Signal Very Good to Weak

I/We are having the same issue.  Worked great  then signal started going from weak, to poor to nothing.  Box was always in the same place, moved it around and now I'm in our detached garage trying to get a better signal and I can get good for a while, then it just drops out to no signal for no reason ...in doing some research, I think the box overheats with too many wireless devices connected to it, but not sure...I unplug, let it cool, even put it in the fridge and can get it back working for a short time (30 minutes maybe) but it goes to no signal again. It's really not usable for anything! Frustrating but I haven't called support because I do not think my problem is unique  nor do I think they have a fix for it. Making decisions