will the mavic auto rotate?? with motors off in the air.

Sorry No! DJI employs fixed pitch props with esc speed control. Remove power and they fall like a rock....

To auto-rotate, you need collective pitch which allows you to change the pitch angle of the rotor blade. With collective pitch, the pilot changes the pitch or angle of attack of the main rotor blades to control lift, while the motor/engine speed and rotor speed stays, more or less, constant.