I put my motivation on the back seat

This jumble was spoken by someone who was relating that she had no been motivated in the past but was now ready to move forward.  It is a mashup of “on the back burner” (postponed or suspended) and “take a back seat” (occupy an inferior position; allow another to be in control).  Both idioms contain the word “back”, causing I suspect the confusion.  Not sure I have left my motivation on the back seat of the car, but certainly my wallet and sunglasses.  A big thanks to Lynn Hannula Johnson for hearing this one and sending it in.