aperiodic

convulsive, sudden, violent

broken, disconnected, fragmentary, interrupted

aimless, arbitrary, desultory, haphazard, hit-and-miss, hit-or-miss, odd, random, scattered, slapdash, stray

capricious, changeful, changing, flickery, fluctuating, fluid, inconstant, mercurial, mutable, temperamental, uncertain, unpredictable, unsettled, unstable, varying, wavering

changeable, fickle, variable, volatile