In general, any cause of death is natural, and all these divisions into "natural" and "unnatural" - just speculation. Old age is not the cause of death, cancer is not the cause of death, it can be caused by, for example, stopping the heart or stopping breathing. Murder is also a natural cause, strangled - pulmonary insufficiency, a bullet flew in - cessation of brain activity. An unnatural cause of death, for example, could be the sudden transformation of all the atoms of the body into gold .. But this is already mythology.