Give warm water

I totally understand your concern. Before suggesting treatment, I would like to ask a few questions to ensure the correct management can be provided. Contact me on Practo or WhatsApp chat. Contact number: 97012307 two nine Dr. G. Avinash MBBS, MD (Pediatrics) Fellowship in Neonatology

Greetings Nighttime cough in a 3-year-old can have several causes and often requires a professional evaluation. The symptoms described are consistent with conditions such as post-nasal drip from a cold or allergies, childhood asthma which frequently flares at night, or gastroesophageal reflux. You should monitor for "red flags" like difficulty breathing, wheezing, or a persistent fever. To help your daughter, you might try using a humidifier, ensuring she stays hydrated, or slightly elevating her head during sleep. Since the cough is persistent and affecting her rest, please consult a pediatrician

Night time cough can be because of tonsils adenoids postnasal drip due to infections and allergies sometimes asthma. Requires evaluation and advice.

A cough that occurs mainly at bedtime, during sleep, and early in the morning while your child is otherwise active and well during the day is often due to post-nasal drip from allergic rhinitis, enlarged adenoids, or airway hyperreactivity/asthma rather than a simple seasonal cough. While occasional coughs can occur with weather changes, persistent night-time cough for more than a few weeks should be evaluated by a pediatrician. Watch for associated symptoms such as snoring, mouth breathing, recurrent colds, wheezing, or exercise-induced cough, as these can provide important clues to the underlying cause.

It's normal only it  could be Post nasal drip, gastroesophageal reflex,  adenoids