Yesterday in Commuting Theater

A man, facing me but obscured by the seat, two rows away in a solo seat, so that only the top of his head and his shoes are visible.

He spends the 40+ minute trip rocking his feet back and forth and arching the tips, as if he was (a) engaged in slow spasmodic dance, (b) engaged in a medical condition, or (c) engaged in a personal condition.

I'm going with (a), since I also saw headphones. But you never really know...