1991 Dodge Dynasty LE car will suddenly die while driving. If I pull off the road, turn the ignition off and restart it- will start but when I put it back in gear the engine stalls again. After five or ten minutes of this it suddenly starts working again and I can drive again. Very intermittant-sometimes it happens two or three times in a half hour, then will run fine.

that would be a good place to start -replace the filter-then if not better do the pump-Denny

tune up - cap,rotor,plug wires.plugs fuel and air filter- you are either losing spark or fuel under load

underneath the engine

You need a new speedometer cable

Not good. I saw nothing about the fan being checked?

I am not really familiar with the setup there but I'd be looking for a second relay to kick the pump on when cranking.

here is what I found:
http://www.the12volt.com/installbay/stereodetail/715.html

I would check the button switch's on each door, If you have a damaged door or one that has worn hinges maybe it has enough movement on the bumps to allow the switch to turn on the lights

my ram 50 starts just like any other vehicle, (no light switch pulling whatso ever), it sounds like somebody haas rewired something wrong or you have a loose connection and when you hit a large enough bump it cuts your power. Start it up and find a speed bump somewhere and drive over it enough to give your truck a jolt and see if it dies.

Hi. I have two Dynasty LE cars, (a 91 and a 93). Both have the 3.3 litre. The 1991 had almost the same problem as yours except it would only do it once the engine warmed up, (similar to your freeway issue, given distance and time for the engine to warm up to operating temp.) I had it in about three shops before the dealer found an intermittent fault with the cam and crank sensors. I replaced them and now it runs just fine. I hope this helps.