intermittent

fitful infrequent occasional periodic recurrent recurring seasonal

alternate arrested broken by bits and pieces checked cyclic cyclical discontinuing discontinuous epochal every other here and there hit-or-miss interrupted isochronal isochronous iterant iterative metrical now and then on and off periodical punctuated rhythmic rhythmical serial shifting spasmodic stop-and-go

constant frequent permanent regular usual

continual continuing perpetual