Sudden lack of energy and sweating may be caused by the following reasons: 1, there may be a sudden lack of blood supply to the brain, such as cervical spondylosis, especially vertebral artery type of cervical spondylosis, compression of the vertebral arteries and lead to insufficient blood supply to the brain. 2, there may be a cardiac problem, such as cardiac arteriosclerosis, cerebral vasospasm and lead to insufficient blood supply to the brain. In addition, cerebrovascular ischemia of the posterior circulation, or cerebral arteriosclerosis, cerebral vascular spasm and lead to insufficient blood supply to the brain, may also occur. 2, there may be cardiac problems, such as myocardial infarction, angina pectoris, or malignant arrhythmia, resulting in a sudden insufficiency of the heart’s pumping, resulting in insufficient blood supply to the brain can also appear suddenly dizziness, cold sweating, generalized weakness. 3, there may be some other problems, including dizziness, cold sweat, and generalized weakness, which may lead to insufficient blood supply to the brain. 3, there may be some other diseases, such as hypoglycemia, hypokalemia and so on, heatstroke will also appear this situation.