When there is a minor child in a hospital, ER. They would probaly be shaking is fear because they don't know whats going on nor what to do. Sometimes a child may be crying, and shaking, while being curled up in a ball. In many cases, children come in and they don't shake, and they get whats needed done, but that's not the case for every child. Some kid's might be having anxiety because, they don't understand. Especially if it's there first time being in a hospital, but for whom has been in the hospital know what to do.
So they best way you would describe a child is: Scared, frighten.