at intervals

gradual

by fits and starts fragmentary intermittent interrupted little-by-little partial patchy spotty step-by-step

betwixt

amid amidst among bounded by centrally located enclosed by halfway in in the middle in the midst of in the seam in the thick of inserted interpolated intervening medially mid midway separating

erratically fitfully haphazardly infrequently sporadically unevenly

any which way anyhow by fits and starts by turns disconnectedly eccentrically helter-skelter in snatches jerkily now and again occasionally off and on out of sequence periodically slapdash spasmodically uncertainly uncommonly unmethodically unpunctually willy-nilly

evenly regularly

every now and then every so often infrequently intermittently now and again occasionally periodically sporadically

at times every once in a while from time to time hardly irregularly not often off and on on occasion once and again once in a blue moon once in a while once or twice sometimes

hardly infrequently periodically seldom sometimes sporadically

at random at times every so often from time to time irregularly now and again on occasion once in a blue moon once in a while once or twice uncommonly

always constantly frequently regularly steadily usually

alternately at times every once in a while every so often fluctuating from time to time irregularly now and then occasionally on occasion once in a while sometimes sporadically vacillating variably

at times discontinuously every now and then every once in a while every so often from time to time hardly infrequently intermittently irregularly now and again now and then occasionally off and on on occasion once in a blue moon once in a while periodically sometimes sporadically

at times every now and then every so often from time to time hardly infrequently irregularly now and again on occasion once in a blue moon periodically rarely seldom sometimes sporadically

consistently constantly frequently occasionally

at times ever and again every so often from time to time here and there intermittently now and again now and then off and on on occasion once in a blue moon once in a while periodically recurrently

never