The main reasons for infants falling asleep with a startle include being frightened during the day, inadequate development of the nervous system, and lack of nutrients. 1. Frightened during the day: after the baby is frightened during the day, it will cause certain stimulation to its nervous system, and this stimulation may last until the baby falls asleep, and the subconscious stimulation that still exists will cause the baby to be startled and startled. 2. The development of the nervous system is not perfect: the baby’s nervous system is still in the stage of continuous development, compared to adults, its nervous system is not well developed, the brain center of the nerve inhibition ability is low, so the baby may fall asleep and have a fright. 3. lack of nutrients: when the baby body lacks calcium as a nutrient, it will cause the nerve potential conduction abnormality, which will lead to the baby fall asleep with a startle. If the infant falls asleep with a startle persists, you need to go to the hospital as soon as possible, by the doctor according to the specific conditions of the individualized diagnosis and treatment plan, so as not to delay the condition.