Very warm bedroom after troubled sleep

Where's the water heater for your apartment? (Or the neighbor's?) Might even have a pipe going by that heats up when somebody uses it.

Other than that, things you're exposed to may cause a sensation of heat. Any chemicals being sprayed around, eating differently, or trying a different soap when taking a shower? (I find tea tree oil seems to be good at dealing with some skin issues, but it also makes me extra sensitive to heat.)