Sudden unconsciousness and quick recovery may be due to transient ischemic attack, vagal reflex or cardiac arrhythmia. 1. Transient ischemic attack: If the arteries are narrowed or blocked due to atherosclerotic plaque formation, blood clots, etc., the blood supply to the brain will be transiently insufficient, which may be manifested as a sudden unconscious fainting and recovering quickly. 2. Vagal reflex: excessive mental stress or blood volume shortage, pain stimulation, etc. will lead to vagal reflex, which will lead to heart contraction and inhibition of heart rate slowing down, blood pressure abnormally lowered, and transient cerebral ischemia, which will be manifested as sudden dizziness and fainting, and then recovered very quickly later on. 3. Arrhythmia: If atrial fibrillation and other diseases attack, the heart beat rhythm is abnormal, the output per beat is reduced, if the situation is more serious, there may be sudden dizziness and unconsciousness. The heart can recover quickly after restoring effective output. Sudden dizziness, unconsciousness quickly recovered from the situation, can also be seen in other causes, it is recommended that timely access to improve the relevant examinations, follow the doctor’s instructions for symptomatic treatment.