Dodge Repair: 1998 Intrepid stalling, miss fire, loose power

Question
I have a 1998 Intrepid 3.2 engine. For the past 2 months I have had a problem off and on concerning the engine dying out. It happens on extended freeway use. After about 20 to 35 miles the engine light starts to flicker off and on and I loose power, the engine dies down and wont accelerate. It will give one jolt and then then the engine quits and coasts to a stop. After letting the car sit for 30 minutes or so it will start right up like nothing has happened and off you go. This dosen't happen all the time since I take this trip 5 days a week but only on occassion. It happened today and when trying to start the engine after waiting it would just sputter and jump the engine gaining only about 500 rpms then would rise to 1000 to 3000 rpms then would die down and eventually quit. I was very tempermental with the gas pedal while the sputtering was occuring. I have had the car in the shop 3 times now. Diagnostics once showed a miss fire code on cylinder #4. I have had a tune up and crank case senser changed out. The mechanics are having trouble figuring it out since the problem isn't happening when I have brought the car in. This last visit to the shop the mechanic put on some testing equipment checking the fuel lines, etc. but couldn't come up with anything while test driving. Any suggestions... The car is on the side of the road today!!!!

Answer
might need to take it to a dealer  and not just some old shop  they are simply guessing at this. With out seeing it for myself  I cant to do to much  things like that could be 20 different things and if u dont know what to look for with a dealer scanner  or any scanner  u are simply guessing.I live in the Atlanta area I would be glad to look at it for u.