my navigation screen blanks out & comes right back on, no matter what i have it on. eg: radio, cd, tape. "BUT" when the car is in park the unit works fine....as soon as i start to drive the whole unit shuts down & what ever i am playing shuts down also eg: radio, cd, tape and comes right back on.......i disconnected the battery & its still doing the same thing, when i first turn the car on i cant touch the screen to operate anything i have to press the manual button. & the screen keeps saying low fuel although my tank is almost full & if i turn the unit off the screen starts back up, the navigation does not come on at all anymore even if i touch the manual button, a few months ago when i tried to press agree on the screen it would say DISK COLD......could someone help me please thanks in advance for your help