I suppose the previous poster thought he has a sense of humour, This heating on the outside wall of a fridge freezer is fairly common. It happens mostly on older models maybe getting down a bit on refrigerant gas which flows through the pipes in the wall to cool the cabinet. It cools quickly once motor stops when the cabinet is cool. It is not going to burst into flames, so don't worry about it.
Lincoln Appliance NZ
February 2009