Heart palpitations.  Often, but not always, harmless.
D001145:Arrhythmias, Cardiac / Q000517:prevention & control*; D003681:Dehydration; D015444:Exercise; D005334:Fever; D015438:Health Behavior; D007722:Health Knowledge, Attitudes, Practice; D006339:Heart Rate; D006801:Humans; D013315:Stress, Psychological