I hadn't seen the Putin video with the hand tremors. That did not look good.
If he has Parkinson's, and he is so vain he wants to appear in public with zero tremor to deny it, then he may be overdosing, which from close family experience I can tell you will absolutely cause mental impairment, daylight hallucination, fear and confusion episodes, etc.
The rest of the gripping and twitching looks as much to me like episodes of intense pain, which if it's his back isn't necessarily anything immediately threatening, other than maybe to opiate addiction. But certainly a tumor/growth anywhere along the spine would be an equivalent to prolapsed discs or spinal stenosis as a source of that kind of pain.
Another scenario that sort of fits is some kind of intestinal condition. Maybe COVID wasn't the only reason he was keeping strangers far away from him. You wouldn't want reports running through the grapevine that dear leader stank.