This symptom can be caused by many reasons, mainly divided into the following aspects: 1. Whether there is a lot of sweating or vomiting recently, especially in summer, it is likely to be caused by hypokalemia. If the symptoms are mild, you can take some potassium tablets with some fruits that are high in potassium: plums, bananas, etc. 2. It may be caused by liver and kidney deficiency, deficiency of qi and blood, you can go to a Chinese medicine practitioner to prescribe some medicines to nourish the liver and kidney and regulate qi and blood. 3. If you have not been relieved, it is recommended to go to a major hospital for examination to prevent myasthenia gravis or other diseases. 4. High frequency of intercourse can also cause the symptom.