If the washing machine reaches the spin cycle without clearing away the rinse water, it is possible for the out of balance weight to unbalance the whole appliance and cause it to walk forward, coming to a stop as the water and waste pipes restrict its further movement. Modern washing machines with their out of balance spin protection should not do this, the electronics aborting the spin programme as soon as OOB (out of balance) exists.

The normal cause of this is a blockage to the drain system, check out the FAQ My washing machine will not drain.