Vet appointment went well, and as he had no symptoms there was really nothing for the vet to do besides poke and prod him.
Her guess is arousal, but found the paw kneading and back leg spasm as not consistent with that, and she did mention a possible seizure.
If it happens again we will film it and email it to her at her request.
I'm going to try to halve his Proin med just in case. His incontinence is mild, just drips, and we don't have carpet so nothing gets ruined.
Appreciate all the contributions.
In general he has been coming along well, his tail wags so much more now, he frolics, gets playful, and will chew on bones now, will rarely fear pee, and doesn't collapse in ball of submission for being called outside.
Heck, he didn't even hose down the vet's office with marking this time.
He is still not really "group friendly" so he goes upstairs when we have guests, and occasionally I will bring him down on a leash if things are quiet. Too many people seem to make him uncomfortable and insecure.