Hi TidalWave,
Most people that talk about sleeping too hot would be describing either a local sensation where part of their body is sinking in to a softer insulating material and producing more “localized” heat (similar to sitting with your back against leather) or an “overall” sensation of sleeping too hot. Both of them would involve more of a sensation of being too hot in terms of temperature and would produce the perspiration that goes with it and wouldn’t be the type of “burning” sensation that you seem to be describing that may be pointing to something else (possibly muscles or ligaments that are out of alignment and the burning sensation that can go with muscles that are being stretched outside of their neutral position).
If it’s just in your spine then I would suspect that it could be an alignment issue more than a “sleeping hot” issue. If your mattress uses thicker layers of lower density memory foam then this would also increase the possibility that you are describing an alignment issue (see some of the comments in post #10 here).
It’s also possible that it could be some kind of sensitivity to the materials in your mattress which is causing the “symptoms” you are experiencing (this would tend to be more of a “prickly” heat).
Of course it’s also possible that it could just be the type of temperature regulation issues that most people experience on some types of mattresses (even though your description isn’t “typical”) and there is also more about tracking down some of the potential causes for temperature regulation issues in post #2 here.
I would certainly try different sheets because some cotton sheets with very high thread counts are not particularly breathable and can contribute to heat issues and if you are using a mattress protector that has a semi breathable waterproof membrane then this could also contribute to temperature regulation issues as well.
I would also keep in mind that in very general terms memory foam tends to sleep warmer than other types of foam materials that are more breathable. Gel memory foam can sleep a little cooler when you are first going to sleep but the benefits of the gel tends to be temporary and doesn’t normally last over the course of the night and once temperatures equalize they can often sleep just as warm as “regular” memory foam (see post #2 here).
Phoenix