Sudden shaking in sleep may be related to excessive mental stress, or it may be caused by lack of calcium, sleep seizures and other reasons. 1. Excessive mental stress: If there is too much mental stress in the near future, the nerves of the brain are in a tense state for a long time and cannot be well relaxed. When sleeping, it may show a sudden shaking in sleep. 2. Calcium deficiency: when there is a lack of calcium in the body, leading to a decrease in blood calcium levels, which can easily lead to an increase in the excitability of the muscle nerves, it may show a sudden shaking in sleep, which may also be accompanied by knee pain, weakness and other manifestations. 3. Epileptic seizures: Some patients with a history of epilepsy may have epileptic seizures during sleep, which may cause sudden shaking in sleep, and may be accompanied by confusion, foaming at the mouth and other manifestations. If the symptoms of sudden shaking in sleep occur frequently or are accompanied by other obvious discomfort, you should consult a doctor as soon as possible to diagnose the cause and then give targeted treatment.