[frostby]

This is strange, but here's a few questions that need to be answered.

I suspect you may have got your acc and constant wires backwards? Do you keep your presets? Are you turning your key past "the normal on"

Your key rests in the forward position when you have the motor running, and the same spot prior to starting the motor-just before engaging the starter. Your deck SHOULD not know the difference. I suspect there may be a 'truck issue' if this is the case -not a deck issue'

Is it related to lights? Did you connect the deck ground to truck dimmer?