You can configure automatically start and stop Oracle XE 18c database on operating system startup and shutdown. See details from installation guide. I did install XE 18c on CentOs 7 and executed steps mentioned in installation guide. When viewing database alert.log after system reboot, noticed that database wasn't actually stopped properly. Processes were just killed. I didn't investigate more why that happens on my system. For workaround I did revert steps mentioned in installation guide and created service file for systemd.