Being a 760, your car came with the Nivomat self leveling system as standard equipment. They should have cost you $350-$500 for a pair without labor. If these are not what was installed, then either the car was converted to standard 740 type requiring different rear springs OR you have the wrong shocks in back which will cause it to ride low and bottom often.

The Nivomats have an accordion boot on their shaft, and appear to be mounted upside-down. I am not sure if the conversion shocks get mounted the same way or as they would in other cars, with the working end down.