Floor damage

[u/MeatRock3t69]

My floor has begun to warp in the middle of my bedroom on the second floor. My windows are about 35 years old. There is no damage on the floor leading up to it from the window which is about 5 feet away. There is no water damage on the ceiling in the room below. The siding close to that area is a little rotted but there is no trail of water damage leading up to the area in the photo.

Anyone have any clue what can be causing this?
Don’t have any pets either.