every now and then

Also, every now and again; every once in a while; every so often. Occasionally, from time to time; also, periodically. For example, Every now and then I long for a piece of chocolate, or We take long walks every now and again, or Every once in a while he'll call, or Every so often she washes the car. The first term dates from the first half of the 1700s, the last from the mid-1900s. Also see from time to time; once in a while.

The adverb has one meaning:

Meaning #1: occasionally
  Synonym: every so often