Vehicle caught fire while driving on highway. The vehicle started to decelerate & would not go over 70 MPH. Driver pulled off at the next exit and turned the car off. She waited about 5 minutes and turned the vehicle back on, Vehicle was now normal, but still would not go over 70 MPH. There were no warning light or anything. Operating the vehicle 70 MPH for about 20 mins and then heard a clicking & banging. Vehicle started to losing speed. Driver turned on the flashers and the vehicle went to just under 45 MPH. Driver decided to merge to the upcoming rest stop. Vehicle then stopped just before the exit and driver got out of the vehicle she felt the hood. The hood was not hot, but saw smoke. Driver then grabbed the latch to open the hood & flames burst out from side to side. Driver put the hood down ran to removed her belongings out. A passerby called the police and vehicle was engulfed with flames.