Based on the video, the vibration is as intense as if he was humping the air. Which is quite bizarre. I don’t think that’s what’s happening, but for those who can’t view the video, that’s a description.
Does he do it only after standing on his hind legs? Based on his reaction from it afterwards, it does not seem like it’s something he’s controlling. He seems confused and turns around to identify something behind him. Perhaps it’s a muscle spasm from weakness of using his back legs. Perhaps it’s a spasm caused by being overly stimulated.
It’s good that you’re going to a vet because this seems like something you’ll need a professional, rabbit-savvy opinion on. Sending you good vibes and keep us updated!
But also maybe air humping? I have just never read anything about it and Wick was not a humpy rabbit. But you mention it occurs after strokig him, so unsure.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.