If something moves jerkily, it does not go smoothly. It starts, stops, jumps, and starts again — like a nervous hand, a car that is still learning, or a film that skips. We use it for bodies, machines, and sometimes speech, when the words come out in little bursts instead of one easy line. It is an ordinary word, not a grand one. Though actually, this adverb is almost always about that rough kind of movement. It does not mean the person is “a jerk” (someone rude). That is another road from the same family of jerk, and jerkily does not carry the insult.

一頓一頓地、不順暢地