The major early symptoms of Parkinson's are: tremor, rigidity, bradykinesia (slow movement) and postural instability (balance problems).
Yep, some combination of these symptoms, but not necessarily all. Moreover, the "tremor" aspect can be varied. SG mentioned head tremors, and we are all familiar with hand tremors, but my Dad had issues where, for example, his legs would just take off out of control. Mom would say, "Why are you walking so fast?" and he'd respond, "I can't help it"
Rigidity was another issue, and that shows up as a characteristic "shuffle" instead of walking. This is where Dad was initially diagnosed, as the neurologist watched him walk. When she pointed it out, it was pretty obvious.
Bradykinesia - sure, but there is always the question of whether it is because of disease or just that they are getting older, so it can be deceptive. However, this was a big issue for my uncle, whose movements got really slow.
And with postural instability, again, old people have balance issues, but it happens. My Dad had an incident before he was diagnosed where he was bringing the boat in from the lake by himself. We don't know what happened, all we know is that he fell and broke his sternum. He may have passed out, or he may have just fallen.
While there is certainly cognitive decline that can come with Parkinson's, I generally figure that is later onset. It certainly is not Alzheimers. Look at Michael J Fox, for example. Serious Parkinson's physical symptoms, but no sign of cognitive decline. Moreover, the cognitive decline that comes often manifests as "sundowners" syndrome, where symptoms are worse at night. My Dad was textbook. He would be pretty normal during the day, but at night he would just lose all sense of reality (you will see commercials on TV for medicines for hallucinations associated with Parkinson's - that happens too). You wouldn't be seeing any sundowner's issues with Biden. Even if they were occurring, they'd just keep him out of view. But there is no reason to think they are occurring.
