Your problem sounds like either an electrical loose connection or a short circuit. If your car has a crank position sensor, I'd suggest you check the condition of the cable which connects this to the ignition system. This cable can deteriorate and the rubber insulation can then crack and fall off. This would allow the wires inside to short circuit and the ignition system would lose the timing signal.

I had this happen on a Volvo. The car would briefly stall and the starting got harder and harder until it refused to start at all. It was the crank position sensor.

I'm not familiarwith you model but my '85 300E has this sensor.

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1986 300E
1993 Volvo 940 Wagon
1984 Volvo 240 (daughter's)
1976 Dodge 1/2T pickup, gas hog