Hi I need help. I bought a 03 350z with stock nav in it and it comes on when it wants. Like if I drive for a hour it will pop on by it self but old after driving for a while .. I check the door sensor to make sure door was on track and hitting it but that's not it .. I can see the screen turn black when I turn ignition on but stays like that till it wants to come on . Also the DVD does not work until it comes on , meaning I can't eject or it does not beep or respond till it comes on .. any idea?

 

Take it all out and throw it in the trash. It never worked well, even when new, and it's surely not worth fixing. Get yourself a good aftermarket headunit, with or without GPS (I'm guessing your phone has that), and get better sound, too. Check your options on www.crutchfield.com

 

Your 2003's GPS is 14 years old... Way past the life you expect for a digital device.

As dcains recommends, replace this with new equipment. You will have a much better solution that costs less and performs much better than attempting to repair and update the antiquated equipment in your car.