Usually that feeling comes from what's called PVC's (premature ventricular contractions). They are very common often can come from stress
, caffine, salt, hyperactive thryroid and other conditions. In younger people and in people without heart disease
they are very annoying but not serious.
Sometimes you may have them for a while they may disappear and reappear at another time. Often it's best just to leave them be without treatment. You're doctor will check you out to be sure that's what they are.