[MargaretR]

I appreciate these constructive comments.
I have only ever experienced static shocks before when removing nylon underwear.
I wear cotton only nowadays. I was wearing a cotton nightie and terry towelling cotton dressing gown when I experienced that mild shock. Although my fluffy slippers are synthetic.

It was a tingle that didn't extend beyond my fingers so, since many people get it, I have decided to diagnose it as static only.

I haven't plugged in that PC tower since then, but intend to.