samsung rl36sbms fridge/freezer. problems.

Hi guys, the fridge and freezer keeps going off, defrosting the freezer and letting the fridge warm up, it all still lights up, and it you switch it off then back on again starts to work and brings the temp down in the fridge and freezes the freezer back up so i think its more a sensor problem, any ideas where to look or what to change? any advice greatly welcomed? Or anybody know a good engineer ini the rochdale area? thanks