"Has anyone ever had a tooth that's heat sensitive and uncomfortable to chew with that has resolved itself without dental treatment of some kind?"
Sort of. My bottom left back tooth had a hole rotted into it by the wisdom tooth, so it got filled, and was fine for a while. Then it got sensitive to bite on, but the dentist couldn't find anything wrong. After about a year or two of complaining it resolved by itself and was OK for years.
Then one day the filling fell out and got replaced with a bigger one. That too was ok for while but then got painful to bite on. After a couple of years of the dentist telling me he could see nothing wrong I was all set to ask him to pull it out when it suddenly broke one day. The relief was instant, after years of jumping through the ceiling I could chew normally again.
That too got filled and was fine, but then one day the dentist told me the filling was leaking and needed to be replaced, but I was so reluctant to go fixing what ain't broke that I decided to leave it while it wasn't hurting.
After a while I decided not to leave it any longer but by then it was past filling, so I got a crown. Now the one with the crown seems to be rotting the one in front of it, just like the wisdom tooth did to the crowned one........