Thesaurus.com
Dictionary.com

once in awhile

ADJECTIVE
every once in a while
Synonyms
WEAK
every now and then every so often from time to time infrequently irregularly now and again now and then occasionally once and again once in a while periodically sometimes sporadically
ADVERB
every once in a while
Synonyms
WEAK
every now and then every so often from time to time infrequently irregularly now and again now and then occasionally once and again once in a while periodically sometimes sporadically