[technics256]

You can do this yourself with Shortcuts app.

Create a timer function to run a shutdown on a time interval you order. Change shutdown to "restart".

[KennyBlanken]

You clearly haven't tried it or even googled it - because it's impossible to do it unattended. A dialog pops up (and only when unlocked) asking you to confirm the reboot. It's probably because they were worried users might end up in a constant reboot/shutdown cycle, though presumably they could just implement a "if rebooted in the last hour by a script, don't allow it again" rule.