Matilda's had a few of these experiences. All I have done is exactly what you've done & that is help them settle once they are able too. Cuddles & holding them until they are able to sleep again. Its horrible. I have often cried with her & hated watching her little body shake & heave with the fear. I often turn on a light & whisper to her that she's safe with Mummy & Daddy now and that we would do anything to protect her.