My two-year old inside/outside cat has gradually developed a twitch in
his tail.

While his tail is held up, he will twitch it by rotating it along its
axis.  Possibly with a slight side-to-side twitch of his hindquarters.

This looked a little bit like spraying behavior, but without the
spraying.  He does it around me.  I haven't especially noticed it while
he makes the rounds of the house (ala spraying).

He is fixed and has never sprayed that I've observed.  Could this be the
gradual onset of spraying?  Harmless mock spraying?  The Pain and Itch
of Hemorrhoidal Tissues?

I haven't noticed any extra grooming or scratching of that area.

ideas?