Off and on for sometime now, I have been having a warm/hot sensation running throughout my body for sometime now. It feels like someone has injected me with hot water or something very not; like its running through my veins. It usually happens at night, when I am asleep; actually that is what wakes me up. I always check my skin when its happening to look for bumps or hives, but nothing. No itching either. It last for about 5 minutes, and during that time, I feel like I am about to pass out; at times even my heart starts to race. Now it has been happening off and on during the day; the "hot sensation", the lightheadedness, then palpitations. The majority of the time, its just the sensation and the lightheadedness. This is really beginning to scare me, because I don't like to be alone when this is going on, and it last about 5-10 minutes. Please help.