smjohnston It is common for me to go 18 hours without using my phone. I got no crash notifications.
If auto reboot is doing this then it's a graceful reboot, so you're not meant to receive crash notifications.
smjohnston You don't need to do anything for the setting to show up, unless you're on a highly outdated OS version or EOL device, in which case auto reboot won't show up if the OS version doesn't have the feature.
What device model are you using? And what is your build number?