Intermittent, recurrent, periodic, alternate mean recurring or reappearing more or less regularly but in interrupted sequence.
Something is intermittent which from time to time is omitted or disappears but always returns.
Something is recurrent which returns or has the habit of returning after omission or disappearance. In contrast, intermittent stresses breaks in continuity and recurrent stresses repetition.
Something is periodic which is known to be recurrent at more or less fixed intervals over a long period of time and which, therefore, can be fairly accurately forecast.
Something is alternate which is both intermittent and recurrent, each in turn with something else. When applied to two contrasted or different things, alternate implies a succession of one after the other.
When applied to things of the same kind or description that follow each other in serial order, alternate means every other one.