Configurations
Scheduled Reboot
Login to your DD-WRT router's web interface
Navigate to:
Administration
Keep Alive
Switch on
Scheduled Reboot
Set it to reboot as often as you like at a time when you're unlikely to miss the Internet for a few minutes (e.g. daily at 3AM)
References
Reference
URL
Scheduled Reboot
https://jamie.evawin.uk/dd-wrt-scheduled-reboot-with-cron-fallback/