Thanks guys. The background is this:

He's about 6 years old but I've only had him for maybe 6 months. I don't think it's even been that long yet. He was in bad shape when I got him and it's been an uphill climb trying to get him better. He has been to two or three different vets, all for the same thing, and has been treated with multiple medications. He has to go back again for another dosage this coming week.
He stays in a tub in the living room, while the rest of my collection is in my bedroom. I don't use anything for him that I use for the others and I wash my hands in between. I've even gone so far as to change my clothes once or twice when he'd had really messy poop. The temps and humidity are fine, those are definitely not the problem. He has his two hides and then some, a "shedding rock" and tons of foliage. The issue is definitely not the set up.

There was no smell freaking him out in the video, he was in an area that he knows well. He was sitting on my jacket in the vid, but even off of the jacket he would stretch out a bit and then fall to one side or the other. He doesn't do this ALL the time, but he does it often enough to have me worried. To some extent, he seems to do it every time I have him out of his enclosure. Some days it is worse than others.

He has not been exposed to any chemicals since he's been in my care. I'm very careful about what I use since I have birds and other sensitive pets as well. I don't even bring bleach into the house.

I'm going to definitely mention the head wobble to the vet, but I wanted to make sure I wasn't going to sound absolutely loony in suggesting it could be caused by the parasites.

(And for whoever asked, no he doesn't stargaze. He can look in any direction he wants, whenever he wants ... his head just shakes when he does it.)