Hot flashes without menopause...?

I'm 46 and a half. I've had all the tests - no menopause or perimenopause. Yet from time to time, and this has been for years, I get so hot that it feels like I'm going to "spontaneously combust!" At night, my body heat wakes me into a fit of throwing covers off me. Yet, I don't sweat. I can sweat because I do when I run. I sweat while I do my hair while getting ready. So, my question is: what are these freaky bursts of heat; and why does my body not perspire to cool me down? Is this a perimenopause/menopause thing? Could the tests be wrong?