The fast heartbeat when you get up from a nap is related to the following reasons: First, the heartbeat is accelerated due to poor sleep and lack of rest. Second, the heartbeat is accelerated due to excessive speed when waking up. Third, patients with organic heart disease, such as rapid atrial fibrillation, frequent premature ventricular beats, paroxysmal supraventricular tachycardia, arrhythmias, etc. suddenly appear, resulting in a fast heartbeat, to be further clarified by an electrocardiogram. Fourth, a fast heartbeat from a nap may also be caused by heart failure.