That is very strange. Even when you fully disconnect power, I think that the nav computer saves your last address. The only time I have seen it fully clear the address input screen is when you reload an OS. I wonder if it is losing power completely when you shut off the car, and it is going through some harsh crash/reboot when you restart.

I would check the blue plug and confirm that the pins that provide unswitched power are actually providing a continuous +12V when the car is switched off.

__________________
SOLD
2000 E38 750iL Highline Edition, Upgraded with the lastest 2006 X5 Electronics
MKIV Navigation, 16:9 Display, Bluetooth, TV/Video with Backup Camera, Sirius, and Aux Input