1994 Oldsmobile Achieva proble starting my car

1994 Oldsmobile Achieva mileage: 108,000. I am having problems with starting my car. I have been to the dealership four times and I am getting frustrated! The car will turn over (crank) but not start. The instrument panel will not light up. The abs, battery, seatbelt and other idiot lights will not light up as well. The first time I kept trying to start the car and it eventual did (ten attempts). The instrument panel lights suddenly light up and the car started without hesitation. I took it to the dealer and they find no computer fault codes. Two weeks later, second time same exact problem so I didn't keep trying to start it but instead had it towed to the dealer. The car of course started fine for them. They replaced the ignition switch but gave no reason why they did this. Three weeks later, third time it wouldn't start, I kept trying to start it, it eventually did (after the instruments panel lights relight) and then the car quit running. It didn't sputter or stall in just quit the battery light didn't even come on. The dealer decides that this problem might be similar to another car (grand am) in which they replaced the car's computer. So, they replace it. Eleven days later I started the car fine drove for fifteen minutes, but when I came to a stop light at a busy intersection and the car silently died. The tachometer went to zero, the oil pressure diminished on the gauge and nothing. None of the idash lights came on, battery, oil light, check engine nothing! I tried to restart it to no avail had it towed to the dealership. They went out to start it, it wouldn't. They got their fault code scanner, fuel pressure gauge, and they pulled a spark plug wire inserted a device and then grounded it to the engine. The car started fine and showed no faults. I think they thought I was lying about the no start but put my car near a shop, mechanic, or diagnostic equipment and it starts without hesitation. The battery is fairly new, the alternator is about a year old, I had a sticking egr valve last summer that caused stalling but they freed that up, the transmission fluid has been recently changed. I maintain my car well. Can you please help me!