Sweaty foreheads and sweating without activity. A common cause is calcium deficiency, which may also be related to body weakness and spontaneous sweating or kidney deficiency. You can eat more calcium-rich foods such as milk, soy products, beef and mutton, sardines, etc. and participate in more aerobic outdoor exercises. If the symptoms persist and worsen, you should go to the hospital for relevant examinations to determine the cause of the disease and then treat the cause.