2017 Sienna. Walked into my garage one night and heard a soft hum. For the life of me I could not isolate the source of the noise. But on a whim I opened and then closed the automatic passenger-side sliding door and the noise stopped. Problem repeated itself a week later. It seems the motor toward the rear of the car is spinning, or doing something, even when the door is closed. That, plus the door seems to open more slowly than it should. Anyone hear of anything like this?
I might imagine that sensor indicating that door is closed malfunctions, so that electric motor keeps trying to close it.
I might also imagine that as motor is getting substantial higher load that usual, it gets worn, probably eventually it will fail.
… and the OP is likely to wind-up with a dead battery in the very near future as a result of this problem, unless it is fixed very soon.