No and no.
I'm not sure what is a "natural cause" in this context, but if it's cardiac arrest caused by age-related dystrophy of the cardiac muscles, then no, there is no suffering, at least not universally: Since age-related dystrophy hits all parts of the body, it's likely preceded by increasing amounts of bed rest, leading to quietly drifting off into the great sleep.
Of course, if you add on other natural causes like age-related diseases or being eaten by predators, the suffering can be great indeed, or not: A tiger will sneak up on you and crush your skull without you ever knowing what happened.
Adding on further causes still, like dehydration or hunger, and the suffering is back.
But is suffering a universal fixture of death? Emphatically no.
As for the "all living things" part of the question, the answer isn't just "no"; it's "that's nonsensical".
By individual count, practically no life is complex enough for suffering to be a relevant concept.
I don't have an exact number for you, because how would I get one, but at a rough estimate, bacteria, algae and archea constitute 100% of all individual life forms by count, and suffering is not a concept that makes sense for them.
If we ignore simple life, even among complex life there is so much variety of capabilities that basically nothing universal exists.