This answer really depends on your age, sex and risk factors. If you are young <35 its probably nothing serious but could be your thyroid
, panic attack
or rarely a heart problem. If you are older, obese
, smoke etc it could be a sign of something more serious in the heart and should be further evaluated by a doctor. Bottom line if you have already been evaluated by a doctor and had a normal EKG its probably nothing but if you are still nervous you can ask for an event monitor.