The Amiga doesn't have a built-in software based routine for restarting (not like Windows does, anyway). You might look at how the installer is attempting to trigger a reboot. FWIW, it can be done easily enough, plenty of small utilities out there that can do it, just there's nothing built-in, per se. See the 1:35 mark in my video, here:
https://www.youtube.com/watch?v=RSzJn9BRHIE