Trans went into limp in mode. After you shut the car off it will drive ok untill the TCM (trans control module) sees a problem. Are you the original owner? If so it maybe warranty. Take it to a dealer so they can scan it. Ask if there are any updates (flashes) for the TCM while you are there. Those are reprogramable and the factory poss has new software so get that done. Those transmissions have most of there problems behind them so let hope it is minor. 1 tip. If its is somthing major and its not warranty. Ask for any warranty assistance, if they are no help call the chrysler 1-800 # in the back of your owners manual and ask for help. Remember to be nice, you get more bee,s with honey!

Also 80% of the time a speed sensor will turn on a check engine lamp, and poss the speedo goes out with it.