DC motor won't spin without a push
You're using far too small a power supply. Apparently it can only provide about 0.5 amps to a motor that needs (nominally) 0.8 amps to run at no load. Worse, at startup the motor will pull stall current (see the specs), for an instantaneous current of 34 amps. 

So basically you need a bigger power supply. A 12 volt, 5 to 10 amp unit sounds about right.