Yes, it sounds as if the auto defrost mechanism has failed or is playing up. My fridge has been like that for years. What I do is turn the fridge off (0 on the dial), pause, and then turn it back on again (I set it to 6 on the dial). This initiates a defrost cycle where the fridge, all being well, stays off (no sound from the pump motor) until the inside has defrosted and then turns itself back on. I try to remember to do this daily. If there is a considerable build-up of ice it may restart before the ice has cleared, in which case I leave it off until all the ice has melted and then turn it back on.