1995 S500 problem

[Pili380SL]

My 1995 S500, 130K miles, has developed a problem. It starts and runs perfectly cold, but after 10 or 15 minutes developes a slight miss which over a few minutes escalates into stalling. The previous owner said that he had the engine wire harness replaced and it shows no sign of degraded insulation. I tried unplugging the mass air flow sensor and it momentarily effects the idle (briefly smoothing out) but then settles right down into the same problem. It did however make the SRS light come on. I searched the forum but could not find whether crank position sensor failure is often related to engine temperature. The plug wires and distributor caps are about 6 months old and I see no arching anywhere. Any ideas? Thanks for any help.