Question mark folder on startup, how can I recover?
The icon you are receiving indicates that your computer is unable to find a suitable operating system (OS).

Your internal disk does not appear in disk utility or diskutil list. Either it is physically disconnected or the more likely answer: dead. I would suggest you bring it into a local Apple Store. The Geniuses will be able to tell you the issue for free. You can decide if you would like to pay to have the disk replaced (assuming death is correct) or to get a new Mac entirely.

Either way you shouldn't lose too much data because you have been making consistent backups very often, right?