A:Answer It would have to do with power supply and demand ( hard wired may only be to key and not continuous power supply) ,,, the cam has a power supply built inside ( Capacitor ) and as the cam receives power from the vehicle, it fills the power like cell up,,,, once this power cell runs down ( say after turning the vehicle off and no continue power is supplied ) and it will eventually but how ever some times it still has power left in it enough so then the cam it notices the power coming in - it will fire right up and work ,,, If the cams power supply is dwindled down to zilch, the cam wont recognize the power coming to it and not turn on and then you have to manually start it up again. The cam is basically like a cell phone- leave it on long enough ,, it needs recharged because it goes dead but the on board capacitor (Battery) charges back up and works at the same time. It may of been hard wired to the switched power and would explain cam still working after shutting off key but latter not working.
Hope I have been able to help some.