I know I'm late to this party. I have 2 cats, and sometimes one of them (who is fixed) gets the big fat scared tail and hunched back. She doesn't hiss, but she does that randomly from time to time. Usually when she is in one of her "squirrely" moods. I also know cats are nocturnal and are more "squirrely" at night. This same cat has found a little cardboard box in the dining room and she runs and what I call "skatingboards" across the room on it. Where she runs full speed, lands her front paws on this little box, and runs full speed across the room with her hind legs only while the box scrapes across the floor under her front paws. She does this activity daily, and its quite loud.
I wouldn't worry about it. Its fairly normal. Cats are just... Strange creatures at times.