​Newborns sleep most of the time. And the usual pattern should be for them to wake up every few hours to eats, have a diaper change or just be alert for a part of the day. However, if your baby rarely alert, does not wake up on his own for feedings, or seems too tired or uninterested to eat, you should consult the pediatrician. This lethargy—especially if it’s a sudden change in his usual pattern—may be a symptom of a serious illness.