"In fits and starts" refers to something that happens irregularly or in sudden bursts, often with long periods of inactivity in between. Some synonyms that could be used in place of "in fits and starts" include "sporadically," "intermittently," "erratically," "fitfully," or "unevenly." These words all convey a sense of inconsistency or unpredictability, and could be used to describe any number of activities or phenomena, from the behavior of a difficult-to-control child to the progress of a long-term project that is plagued with setbacks and delays. Whatever the context, the phrase "in fits and starts" and its synonyms all convey the idea something is happening, but not in a steady, continuous way.