If you slowly rotate the motor by hand if its got brushes, the resistance of the windings will "jump" as the brushes move from a commutator section to another one. If its got 4 wires and no brushes, then it must be some sort of AC motor or switched DC (AC with square waves!). Conventional single phase AC motors use a start capacitor in series with a start winding, which puts a big phase shif in the magnetic field to make sure the motor starts in the required direction, reversing this winding cause the motor to run in the oppersite direction. Its a fact that these motors are normally limited in the number of starts they do in a given time, as the start current will overheat the start windings. Once the motor has reached 80% or so of its speed a switch on its shaft will disconnect the start winding.
Frank