We had the same issue with ours. Car would start to shudder violently at 40-60 mph for 2-3 minutes and then it would quit. Dodge checked the tires and steering. Of course they found nothing. Then it eventually threw a code during one episode. Of course the PCM didn't store the code so again they could do nothing. Yesterday it did it for me for the first time. 3 miles from home it starts to shake and then the CEL comes on (flashed 12 times). Took it straight to Dodge and they were finally able to pull a code. Cylinder #5 misfire. I'm guessing it has a bad ignition coil. Should find out tomorrow. Hope this helps.