system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do we get hotter when we sleep?

I could be laying on the couch perfectly comfortable.  But if I fall asleep, I'll often wake up hot and sweaty.  Why do we apparently get hotter while we sleep?
gpt
The body cools during non-rem (light) sleep, but rises during rem (deep) sleep. Overall though, your body temperature probably drops about 2° overall through the night.

Do you use blankets? It takes time for your both warmth to heat up the blankets and bed. It feels cool initially, while you're falling asleep, but overtime it warms up. Since your body is about 98.6°, your bed will eventually rise from ambient room temperature (~70°). As the temperature of your bed rises, so does the temperature of your body, since it is harder to lose heat. Your temperature keeps increasing until your body can't cool itself anymore by touching the sheets and mattress. After this, your body will sweat to cool itself down.