Is it sleep apnea? Even infants can suffer from this. One of mine did. It especially affects those with small, turned up noses.
Another thought. A diet high in sugars could be responsible.
Hello and hope you are doing well.
Certain sleep disorders and nasal congestion can cause difficulty sleeping in children. Also anxiety or stress is known to promote lack of sleep. Have an open discussion with your child and help her with any issues that might be troubling her. Many times parents tend to get stressed that the child is not sleeping well and communicate this anxiety to the child which forms a vicious cycle, so relax and let bedtime be a pleasant experience then a task which needs to be completed, tell her good relaxing stories or let her read good books prior to sleeping.
Avoid caffeine rich drinks before bedtime. Ensure to see she plays adequately during the day, as good exercise promotes good sleep. Always make the bedroom environment very cool, dark and cozy like a cave, cause bats are super snoozers and they sleep in caves. If the problem persists consult your doctor. So, Hope this has been helpful and do keep us posted. Regards!!