My husband has had two similar spells, always in the late evening after falling asleep. He says he becomes very warm and then gets chills and breaks out into a cold sweat all over. Seems to loose conciousness. 1st time he urinated when passing out. Called ambulance, spent night in hospital. No answers other than its not his heart. This time it came along with severe muscle cramps in his legs. I towel dried him, kept him warm, gave him water and shook him continuously for about 10 minutes to keep him awake. It then subsided and he seemed to sleep well the rest of the night. fine this morning. He spends a great deal of time in the hot sun doing landscape and yard work.