Unusual vibration resonance in drive

[alexhpilot]

Hello all,

Apologies if this issue has been answered already.
I have recently acquired a 2nd hand 640d convertible from BMW approved used. This is the 3rd 640d I have owned in 6 years, the previous 2 were GCs. Both ran very well. My current one has 34k on the clock. Tracking was out on the right wheel but no big deal.
I have noticed that when in drive gear, there is an unusual vibration resonance when stopped with my foot on the brake. The resonance changes very subtly from time to time. It can be felt though the brake pedal and through the steering wheel. It's a little annoying and something I never had on my previous 2 GCs. BMW are taking it back to look at it. Any thoughts on this?
Please let me know if it requires further explanation.