In the beginning my 159 was pretty good in terms of (the absence of) rattles.
But over the last two years light rattles developed, which sounded like loose interior trim. First from the direction of the off-side rear, later from the direction of the driver's door.
For a long time I couldn't locate it (and it wasn't that bad, to be honest).
Very early on I had the feeling that the doors might not fit perfectly, but pulling or pushing at the door during the rattle didn't make any difference, so I didn't continue that route.
Sometime later (for different reasons) I decided to give the door rubber seals a treat by rubbing them in with silicone spray.
Suddenly the rattle from the driver's door got a lot worse and really annoying. Cleaning the seals off with alcohol made it a bit better again, but not enough.
In the end I treated the seals with a specific plastic- and rubber care product from Sonax, that had been lying around for many years, and luckily that did the trick.
Silence is golden, indeed.