head unit power problems

If all you have is a head unit, check your power wire or ground to the deck for a bad connection

Yes, that is what it looks like. If your car has -ve ground (most cars have -ve ground), then check the positive wire might be loose. If it is +ve ground then check the -ve wire might be loose. Reason why I say this is because the ground usually is ok since you screw the head unit with screws onto some metal part of the car and that should be ok. If you have access to a VOM then you can check to see if your head unit has no diference in voltage from the chassis, and make sure the other cable, -ve or +ve is giving a constant voltage once you car is started (or in acc mode). If these are ok too then your head unit might have a loose connection inside, such as a loose contact on the PCB or something in whcih case you can either repair it (if you are comfortable with soldering irons) if nto then you might have to have it repaired. Hopefully it is just one of the cables. mark