2004 Sienna Steering Noise

I have a 2004 Sienna. When I turn the steering wheel left or right when car is moving, there is a squeal coming from the steering wheel itself. Anyone have any ideas what that might be?

No noise when car is not moving and just turning steering wheel.
No noise from serpentine belt or other noise underhood.
Sitting at driver's seat just turning wheel does nothing.
Move the car and turn, then hear the squealing.

Is it just a matter of lubing or do you think it is a more serious problem?

Thanks.