sporadic -
recurring in scattered and irregular or unpredictable instances; "a city subjected to sporadic bombing raids"
continual occurring without interruption; chiefly restricted to what recurs regularly or frequently in a prolonged and closely spaced series; "the continual banging of the shutters"
noncontinuous,
discontinuous not continuing without interruption in time or space; "discontinuous applause"; "the landscape was a discontinuous mosaic of fields and forest areas"; "he received a somewhat haphazard and discontinuous schooling"
infrequent not frequent; not occurring regularly or at short intervals; "infrequent outbursts of temper"
