Navman S50 How long does a Navman take to power up on vehicle charger.We used it for the first time today, drove 30klm and then drove home and it kept turning itself off.

My Navman S50 has been working fine the other day it decided to show me the safety agreement when switched on then shows half the screen black with navman S50 printed in the black section the other half shows a picture of a pretty womans face looking backwards from a car window. I can get to the main menu and then takes me in a circle back to the safety agreement I've tried resetting by holding the on off switch down for 6 seconds when switching off the device is there any other way to reset my navman S50.