Unfortunately it can be a bunch of things.
Use the videos in this library
AppliancePartsPros's Channel - YouTube
to open it up and check out the pump, coupling and see if the transmission is hanging up in some manner. (I am assuming that it fills).
It can also be a problem with the capacitor (unusual), the motor or the timer. If you cannot find anything wrong you are going to have to just start replacing parts and see which one fixes it.
Sorry not to be more definitive, it's the nature of your problem.