Other brands of cars have been affected by this problem due to floor mats that have gotten too close to the throttle pedal and interfered with its movement. Another possibility is a malfunctioning throttle pedal module (mounted at the pedal) or a sticking throttle plate.
I would check to see if the throttle pedal retracts properly when released. Try fully depressing it by hand with the car turned off and quickly releasing to see if it returns to its original position. Example: