A healthy person can generate enough heat to survive, in other words maintain core temp, if they have enough calories. Above the freezing point there is no chance of frostbite to the outer skin so it will be uncomfortable to say the least but circulation will be more in the core body and less in the skin. Australian aboriginees often slept mostly nude with minimal shelter in temps not much higher than freezing, sometimes with a little fire sometimes without. It would be a profound mental transformation to learn to be able to sleep not when you are a little cold but completely cold all the time. The stress both mental and physical would probably shorten your life.