A four-month-old baby waking up all the time during sleep is considered to be related to diet, environment and vitamin D deficiency. 1. Diet: Babies eat regularly, if they eat too much or too little, they may wake up all the time during sleep because of bloating or hunger. 2. Environment: four-month-old babies are more sensitive to the environment, if the sleeping environment is noisy, the temperature is too high or too low, it may affect the baby’s sleep, resulting in always waking up when sleeping. 3. Lack of vitamin D: If the baby lacks vitamin D, it can cause the cerebral cortex to be excited, which will affect the baby’s sleep, and the phenomenon of the baby always waking up. Four-month-old baby sleep always wake up, there may be other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause, under the guidance of the doctor’s treatment.