It is a dangerous situation, so I hope one of the techs will confirm, but it sounds to me more like a cracked solder joint in your fuel pump relay. My next guess would be something to do with fuel pressure such as clogged injectors, fuel pressure regulator, accumulator, check valve(s), fuel pump(s), or gaskets. Hope you find the problem easily, Andrew Seidel.
85 500SEC Lorinser
83 300D Turbo