Sometimes, but not often
sometimes adverb
on some occasions or in some situations, but not always
occasionally adverb
sometimes, but not frequently or regularly
intermittent adjective
happening sometimes but not regularly or often
infrequent adjective
not happening very often, or not doing something very often
sporadic adjective
not regular or frequent
spasmodic adjective
happening for short periods and not often
occasional adjective
happening sometimes, but not frequently or regularly
every so often phrase
sometimes, but not frequently
(every) now and then/again phrase
sometimes, but not regularly or often
from time to time phrase
sometimes, but not often