What does Marcus Aurelius say about death being natural rather than shameful?

Marcus does not argue that death is good. He argues something narrower and more useful: that death is not the kind of thing that can be shameful, because it is simply nature doing what nature does.

Death as decomposition, not disgrace

In Meditations 4.5, Marcus writes that death "is such as generation is, a mystery of nature; a composition out of the same elements, and a decomposition into the same" (Meditations 4.5). Birth assembles you out of matter that already existed. Death disassembles you back into it. Neither event is an insult to you, because neither is anything other than the ordinary working of a physical world you were always part of.

From this he draws the conclusion he actually wants: death is "not a thing of which any man should be ashamed, for it is not contrary to the nature of a reasonable animal, and not contrary to the reason of our constitution" (Meditations 4.5). Notice the structure of the argument. He is not saying death feels good or that you should look forward to it. He is saying that shame is the wrong category to apply to it at all, because shame belongs to actions that violate your own nature or reason, and dying does neither.

The common misreading

People often hear "memento mori" and assume Stoicism treats death as something to master through willpower, a fear to be gritted through. That is not what is happening here. Marcus is not steeling himself against a real evil. He is correcting a mistaken judgment: the belief that death is bad, or shameful, or an affront to be resisted. This connects to a claim Marcus makes elsewhere, that death is something that happens equally to good people and bad people, and so cannot itself be what makes a life better or worse (Meditations 2.11). If death fell only on the wicked, or only on the foolish, you might have grounds to call it a punishment or a shame. But it comes for everyone regardless of character, which is itself evidence that it is neither good nor evil, just indifferent, like health or reputation.

What changes if you take this seriously

If death is not shameful, then a great deal of the emotional weight people load onto dying, and onto the deaths of others, is imported rather than given by nature. You can still prefer to live longer. You can still find loss painful. But you no longer have to treat mortality itself as an indictment, of you or of the universe. That frees attention for the thing actually up to you: how you act while you are alive. Marcus makes this move explicit when he says that since you might leave life at any moment, you should regulate every act and thought accordingly (Meditations 2.11). The point of remembering death is not dread. It is seriousness about how you spend the time you have.

A concrete way to use this: the next time you notice a flicker of shame or dread attached to aging, illness, or the thought of your own death, ask what judgment is doing the work. Marcus's answer is that it is happening exactly as nature intends, no more shameful than the process that brought you into existence in the first place.