I own a 1989 260E, I get a shuddering/helicopter noise accuring when driving, happens randomly at various speeds, anyone got any possible causes and remedies.

Thanks Scarfletch

 

check the insulation above the drive shaft...sometimes it falls down onto the driveshaft coupler/flex disk and makes noise kind of like your describing.
maybe belly pan flapping under the car?
also air pump as stated from previous poster.