what are the symptoms of a faulty accelerator pedal switch?

What is your question?

My 2006 hyundai azera likes to sputter and shake while at 55mph and or almost throwing you into the windshield. Then it will down shift into third gear and stick there and the check engine light will illuminate. If you pull over shut the car off the car resets itself and is not stuck in third gear anymore. And then the check engine light goes off? HELP