Here are some examples of how you might use "off and on":
* "I've been feeling a bit under the weather off and on this week." This means the speaker hasn't been consistently sick, but has experienced periods of illness throughout the week.
* "We've been working on this project off and on for the past few months." This suggests the work on the project wasn't continuous, but happened in fits and starts.
* "The rain has been coming off and on all day." This describes a day where it rained intermittently, rather than steadily.
Essentially, "off and on" implies a pattern of activity that is not consistent or continuous.