WordNet (r) 3.0 (2006):

jerkily
    adv 1: with spasms; "the mouth was slightly open, and jerked
           violently and spasmodically at one corner" [syn:
           spasmodically, jerkily]
    2: with jerking motions; "She rose stiffly, jerkily from the
       window seat"

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "jerkily":
   at irregular intervals, at random, brokenly, by catches, by fits,
   by jerks, by snatches, capriciously, desultorily, disconnectedly,
   discontinuously, eccentrically, erratically, fitfully,
   flutteringly, haltingly, in snatches, in spots, inconstantly,
   intermittently, irregularly, lurchingly, nonuniformly, off and on,
   patchily, quakingly, quaveringly, quiveringly, roughly,
   saltatorily, shakily, shudderingly, spasmodically, sporadically,
   spottily, tremblingly, tremulously, uncertainly, unevenly,
   unmethodically, unpredictably, unrhythmically, unsteadily,
   unsystematically, variably, waveringly, whimsically, wobblingly