Not too sure about your model quoted,but I think that there is a component fitted to your machine called an "unbalance sensor".
If one is fitted ,it`s purpose is to detect any seriouse imbalance when the drum starts to spin,if it does detect a vilolent thumping then it will shut down the motor to a slower/safe speed.On some models it will shut right down and then switch back in to carry on with the cycle.
In theory it is shutting down to allow the wash to re-settle,and then tries a re-start to see if the wash is ballanced enough to allow to go to full speed.A faulty sensor can sometimes fail alltogether(open circuit) and wont allow the spin cycle to initiate.
My own machine tries to jump out of the window sometimes.It doesn`t have a modern sensor fitted.
Phil.D.
February 2010