Ever burnt yourself on a hot cooking plate?
Imagine a room with said plate as floor and it will slowly increase in heat over time.
No objects in the room, only a big floor, walls with no windows and some heat resistant lights. And roof, obviously.
As it slowly increase in heat, your body want to move away, but anywhere you go, it's the same.
In the end the muscles in your feet can't take it anymore and you might drop down on your knees or your back. Slowly, being boiled alive.
Of course this is more of a mad man trap, not a realistic death senario.
For a more realistic senario, I would say being chased by a shark and devoured. But that might be more of a specific thing for me, due to my fear of deep water and what you can't see.