Your baby should be alert and responsive when awake; you will notice that baby will keep their fists clenched, elbows bent, hips and knees flexed. They will hold their arms and legs closely to their body. Babies are born with primitive reflexes, due to immaturity of their nervous system; arms, legs and chins may tremble or shake when they cry or are agitated. This is all normal behaviour.
Click link for: NHS Your Newborn Baby