Option to enable automatically rebooting the device when no profile has been unlocked for the configured time period to put the device fully at rest again, which is enabled by default at 18 hours. This can be configured at Settings > Security > Auto reboot.
But it’s a security measure to get it to BFU, where data is at rest and secure, in case your phone is out of your possession for an extended period of time (someone steals it, police take it, etc) so it becomes harder to exploit. I’ve set mine to 12. Some do 4 or even less. Feel free to turn it off.
https://grapheneos.org/features#auto-reboot
But it’s a security measure to get it to BFU, where data is at rest and secure, in case your phone is out of your possession for an extended period of time (someone steals it, police take it, etc) so it becomes harder to exploit. I’ve set mine to 12. Some do 4 or even less. Feel free to turn it off.