Chris, I think that a lot of us in cold climates see electrical gremlins related to temperature. This is the season, for instance, when instrument panel lights may only come on when warmed. (Reported several times lately on this board.)
Or when a fist strikes the dash appropriately. (Don't say I said so.)

Why? Poor grounds become poorer (more "iffy") when subject to expansion and contraction.

Time to pull the instrument panel yet again in my car. This time I will get it right... knock on wood!

Your radio: while I have not yet pulled a Volvo radio, I have seen enough of the green manuals and the TSBs that show that *radio grounds* were a problem. Can you clean them up, those grounding wires from the radio's chassis? My unreliable memory says that Volvo may have even suggested (in a TSB) running an additional wire from the radio to... well, some good ground.

Let us know what you find, and someone more experienced than I can help, or I can look around this *(&^pile for the info.

Gregg in MN