I had the same problem in the summer. It was caused by the integrated fridge compressor motor overheating and cutting out. The guys who fitted my fridge boxed it in and left no ventilation for the heat to dissipate. The motor was getting too hot and kept reaching its cut out temperature. If you suspect the same problem, take the fridge out from under the kitchen surface and point a fan at the compressor. If it stats working properly you will need to look at putting a vent in the plinth adjacent to the fridge - I'm only an amateur so use this information on this understanding.
DIY Dave, July 2010