On the way home from London the other day, my previously whisper-silent car started to buzz in two places: the window surround, just behind my right ear, and the dashboard somewhere, just in front of where the passenger sits.

Why do cars do this, and what can I do to suppress the buzz? I know that if I press the bit around my window, I can stop it, but only as long as I keep my hand there. Are there any other solutions, especially for those instances when it is difficult to identify precisely where the buzz is coming from?

No one else got the buzz?

A mate used to stick a folded beer mat in the window trim of his Scooby to stop vibration…
Not much help sorry.
May be that your trim is weathered?

Can often be temperature related. I’ve driven cars that buzzed after being parked out all night in sub-freezing temperatures and were then silent when warmed up after a few miles. I’m assuming it’s all about expansion and contraction of materials.

Without stripping down trim and tring to locate the root cause then you’re unlikely to be able to robustly fix the issue.
Interior trim really isn’t as scary as it looks. I work in the industry and the majority of parts, if there are no screws visible, will simply pull off (normally with a force just below where you’re convinced it’s about to break!).
It’s possible that a scew has come loose or a bit of dirt/stone has made it’s way in somewhere and rattling about.
As scotroutes says, it could be simply temperature driven. Have you had the car through a winter before or is this the first?

It’s my first winter with the car, so yes, you are probably right.