When a child has a startle reaction like this, it should be considered a startle. Generally, a three-month-old child’s ability to accept things is limited, so he or she will have a startle. It is recommended to let the child sleep on the mother’s body. If you don’t get relief, you can go to the hospital for a vitamin D test to check for vitamin D deficiency and then give the right medication to treat the symptoms, which should provide further relief. When the baby is jumping, the mother can use her hands to soothe the baby or stroke her hands to give the baby a certain sense of security, so that the baby can be quiet and the mother can be completely assured that the baby’s jumping will not affect its future development.