Vehicles Moves In "N" Position
WARNING: This page is about a different car, the 2002 Mazda MPV. However, it is still accessible from the selected car via links, so may be relevant.
Possible cause: clutch burned (low clutch, low one-way clutch, low and reverse brake), line pressure low, faulty control valve body, gearshift lever position disparity (although the gearshift lever indicator shows "N" position, hydraulic circuit shows "D" or "R" position).