In general, motors take much more current when they are stopped than when they are running. This is because, when a motor is running, the motion produces a "back-EMF": a voltage which is created from the motor basically acting like a generator while it spins. Due to its polarity, this back-EMF reduces the current flowing into the motor (effectively, the voltage driving the motor becomes Vsupply - Vbemf; less voltage means less current). When a motor is stopped, there is no back-EMF to impede the current flow, so you simply have 3.3V directly across the motor windings; lots of current flows then.