Husband’s Annoying Swaying Back and Forth

My husband is 75. Within the last couple of months he has started swaying back and forth whenever he is standing and sometimes when sitting. His feet stay planted, but his body rocks back and forth. I pointed it out to him with concern, but he continues to do it. I asked him to ask his physical therapist about it, which he did, but nothing has come of that. I’ve stopped asking him about it, but I find that it annoys me more and more.

Recently, we were sitting on a bench waiting to be seated for dinner in a restaurant, he started rocking and he nearly caused me to fall off the bench! I have looked online for answers but have found nothing that seems to fit. He does not display any signs of dementia. Please help me deal with my annoyance at this. I don’t want to nag him, but I’m also concerned. He seems oblivious to it when he is doing it.