Hillary Clinton has seizure / convulsions - tries to play it off by making fun of seizures
Hillary had some sort of neural response triggered either by the sudden burst of noise and motion from the reporters just at the outside edge of her peripheral vision or from the the sudden motion of turning her head in response to that burst of noise and motion .
The response event was relatively brief and mild.
Hillary's response suggests that this is a common enough occurrence that she has the outward symptoms down pat and has practiced a recovery response and follow on exaggerated intentional replay that would disguise the event as goofing around with the reporters in case it ever happened in public .
Notice the two phases of the event , the first looks like an involuntary physical seizure, black out or palsy type event response while the second phase looks like intentional controlled humorous , goofing off type replay of the first involuntary event , combined with humorous comments to reinforce the perception of goofing off.
This was a well rehearsed and well coached recovery from some physical malady intended to disguise the malady for damage control purposes and make light of it in case and event were to ever happen while Hillary was in a public setting with cameras running.
A good example of this type of recovery strategy by a public figure is Micheal J Fox who is valiantly dealing with an advancing case of Parkinson's Disease. When Mr Fox has an event in public he rolls with the punches and improvises a follows through to minimize the event and make it look as normal and benign as possible.
It appears Hillary was doing something similar in the video
.