most likely youre getting PVCs or PACs (premature ventricular/atrial contractions). but im not a doctor so maybe you should see one to make sure thats the problem. theyre scary since you constantly feel your heart stop but they are harmless in the vast majority of people (ive heard something like 70% of people get atleast 1 a day) but sometimes it can mean you have a bad valve or electrolye imbalance something so if you get more than just a few per day you should have them checked out with a cardiologist to be on the safe side. stress, caffeine, lack of sleep, smoking, alcohol are some of the common triggers that aggravate them, look them up on the internet. if you get hundreds a day like me or if they really bother you they can put you on a beta blocker that can help to reduce them