1. spasmodic; uneasy; agitated
1. That night, after being present at his wife's deathbed, he fell into a fitful sleep tormented by nightmares.
2. intermittent; occurring at intervals
2. The wind came in fitful gusts, and torrential rain poured down.
erratic, fitful, intermittent, sporadic
Think about someone getting fits. he does that intermittent action. it comes all of a sudden I am fat and so trousers occasionally fit me fully. So its like sometimes yes and sometimes no.