There is no way for anyone on a message board to tell you that it is nothing serious. You need to be checked by a dr. Have you been told you have Cardiac issues??? If so, this may be a sign of a condition worsening or if not it might be your first symptom in being diagnosed with something serious.
Everyone will have moments of rapid heart beats for many different reasons and not all of them are even health concerns or risks, but if while they are happening and you are feeling bad for no reason whatsoever or they last longer than a few minutes it is concerning enough to at least get checked out.
Hope everything checks out ok, but it is much better to be safe than sorry