A hypnic jerk, hypnagogic jerk, sleep start, or night start, is an involuntary myoclonic twitch which occurs during hypnagogia, just as a person is beginning to fall asleep, often causing them to awaken suddenly for a moment. Physically, hypnic jerks resemble the "jump" experienced by a person when startled,[1] often accompanied by a falling sensation.[2] A higher occurrence in people with irregular sleep schedules is reported.[3]

I hate when I have a hypnic jerk! Don't you?

Does it apply in the same way one would fall asleep in a chair? There are times I do find myself sleeping ( or going into ) in my chair, then suddenly I'd get a 'violent' jerk that suddenly wakes me up, feels like I was about to fall off but I didn't

Yes. Doesn't matter where you are, it's when you are falling asleep and/or may even already be asleep, then
suddenly, your entire body jerks awake. It is kind of a momentary weird feeling.

It is my first time to hear the term. Is it similar to a muscular tick?

I don't think so. I think a muscular tick can happen at any time, awake, moving, walking, etc.

Whereas the 'jerk' happens when you are either asleep or falling asleep.