Adverb
with jerking motions
with spasms
Source: WordNetShe rose stiffly, jerkily from the window seat Source: Internet
the mouth was slightly open, and jerked violently and spasmodically at one corner Source: Internet
His quick transparent lines have the nervous and contracted strength, move as jerkily and intently as a bird." Source: Internet
The Moon appears to move jerkily, and the phases do the same. Source: Internet