Noisy neutral: I had this problem on my 240D. I actually had my throw out bearing split into two and 1/2 of it sometimes remained in the pressure plate causing a slight imbalance. I was also told that the same noise would occur if the flywheel was slightly out of balance.

My symptoms were:
Noise when the transmission was in neutral
Noise goes away when the clutch was depressed
Noise is not noticeable when gear train is under power (driving)

It was the strangest sight to see the throw out bearing split in half, but the clutch was original and was over 40 years old.

Dave