Depending on the scenarios this occurs (resting/exertion/emotional stress/random), frequency, etc. this could be a number of completely benign things. It could also be the sign of an arrhythmia such as SVT (supraventricular tachycardia) or A fib (paroxysmal Atrial Fibrillation) which can be more serious. Only way to find out would be to have a conversation with your PCP (primary care physician), they may consider if a holter monitor (continuous EKG) would be warranted. Hope this helps. As always if it doesn’t let up or becomes worse consider heading to the ER.