Talk with your doctor - if your child is having very disturbed sleep, an assessment by a specialist in child health could be of use, and maybe a referral to a Sleep Disorders
[cyh.com]
Night terrors and other sleep disturbances, such as somnambulism, are disorders of arousal (Broughton, 1968; Fisher, Kahn, Edwards, & Davis, 1973; Guilleminault, 1987).
[ncbi.nlm.nih.gov]
[…] pavor [ pa´vor ] ( L. ) pavor diur´nus attacks of anxiety in children during a daytime nap. pavor noctur´nus a sleep disturbance usually occurring in children and characterized
[medical-dictionary.thefreedictionary.com]