Restarting and factory resetting your Google Nest camera or doorbell will have different results:
Restart: Keeps all your settings, and it should reconnect to the same Wi-Fi network. This is helpful if it ever becomes frozen, has trouble reconnecting to the internet, or isn't working normally.
Factory reset: Erases all your settings and options, and restores its factory default settings. It will not automatically reconnect to Wi-Fi and you'll need to set it up again.
You can find this information, plus additional information on this process here.