Answer:
You write on me and secrets I can keep. In places never seen. I spin like a top. Though stiff as a board I'm often described like a mop.
What loses its head in the morning but gets it back at night?
I cause involuntary movements in your vehicle
What has no beginning, end, or middle?
The more you take away from it the larger it becomes. What is it?
A little house full of meat, no door to go in and eat.