Immediately fall asleep suddenly palpitations wake up heart thumping cause of arrhythmia, vegetative nerve disorders and so on. 1. Arrhythmia: It may be due to the heart beating too fast or too slow heartbeat that causes palpitations, or it may be the rhythm of the heart beating is disturbed, such as arrhythmia. It belongs to the factors of pathology and is mostly seen in various heart diseases. 2. Other pathological factors: it may be caused by thyroid problems or anemia. Detailed examination should be carried out in the hospital for clear diagnosis. 3. Vegetative nerve disorders: cardiac neurosis can occur if one is overworked during the day, or suffers from insomnia or anxiety. Usually, there is no organic disease after examination, and it is caused by unstable nerve function. If often happen immediately fall asleep suddenly palpitations wake up heart thumping should be timely to the hospital.