Samsung SRL3616B works for few hours then stops?

I have a fridge/freezer which will work for a 5-10 hours and get down to temp but then stop working ( lights on but compressor and fans off). If I switch off at mains it starts working again. Reading a few sites I have replaced the defrost heater and termostat but that has not fixed the problem. One thing I did notice is the compressor gets very hot and the side of the fridge get very warm.
I am thinking that it is going into some kind of safety shutdown and is the reason it will work again after powering off.

Thanks