I was taking my 2014 Volt into work today. I was driving out of the neighborhood at about 25 MPH when I felt a lot more resistance and the check engine light came on. I slowed to a stop for a stop sign and the car struggled to hit 15 MPH after that. I basically had to keep tapping the accelerator to just keep a steady 8 MPH. On Star had trouble diagnosing. I went to move my volt for the tow truck and the check engine light was off so I just drove to work. I plan to take it into the dealership but any ideas?