Create an autosave/checkpoint feature for my game?

People tend to make t$$anonymous$$ngs too complicated. The question you have to ask yourself is, what's the absolute minimum amount of data that you can save and still be able to reconstruct the savegame effectively? In some games, like Prince of Persia on the Nintendo, that can be as simple as a 9 digit numerical "passcode". What's the data that's needed there? Stage number, checkpoint number wit$$anonymous$$n that stage, total time left, and a flag that says w$$anonymous$$ch health boosts you've gotten. That's it.

The breadth and depth of your save functionality depends on the needs of your game- most games aren't completely linear like the original Prince of Persia game, and so most can't be saved into a 9 digit numerical passcode. But it's usually not that much harder. Figure out what all you need, and make a data container type for all of that (literally just call it GameDataContainer or somet$$anonymous$$ng). When it's time to save, fill that container with all of the data it needs, serialize it into binary, JSON, XML, or whatever you like, then write it to the disk. None of your scene objects need to be "saved" per-se, you only need the data that's required to reconstruct those objects at a later time.

I have no idea what the specific needs of your game are, so I can't really be more specific. There are tons of threads / guides around for how to serialize / write to disk / load from disk / deserialize- it really isn't much more complicated than that, just make a choice between binary (1s and 0s), JSON (strings, useful for storing on web servers), or XML (human-readable), and then run with it.