lower the passenger seat to its lowest position, this helped in my case.
And I dare to repeat, but the run flats 'steel' tires are not helping here either. I have sleepless night until I wil have my non-runflats on...

But the 2nd row seats can't be lowered .... Why... Why .... I need a Cayenne ....

The cause for the Vibrating/Shaking seats is your rear wheels and tires are out of balance. get it check.

No that is definetely not the reason. Probably the firm suspension and poor design.

Vibrating/Shaking seats

I thought that this was going to be about a new option for the 2009 model year!

Any dealer comments on this problem yet?

I thought so too. But I didn't feel fresher after seating on them and so concluded that it wasn't a massaging seat. :)

Vibrating seats? Sounds like and option BMW forgot to charge you for. Just kidding.

Have you had it at the dealer yet?

Not yet. I was at the dealer but for other noise that occurred around the door trim. We finally found that the noise was only present when the window is fully up. So they applied some tape on the body frame where it meets the upper part of the door frame. The noise was gone.

I'll update you guys with the vibrating seat problem.