In a 1994 'S' class (W140), the old overprotection relay has evolved into the Base Module. That is the unit at the back of the module box that has the 3 or 4 fuses in the top of it. But I doubt that would help with your stalling problem, unless perhaps you have jump started the vehicle and a fuse or two is blown.
Items to check? Perhaps the basics: coils, fuel pressure, MAS, and a stuck open purge valve should not be overlooked.