I’m not sure if this is the right post for this. But looking over the Install instructions, https://github.com/Sonarr/Sonarr/wiki/Installation, it is missing the instructions for having the service auto start. (At least in a Ubuntu/Linux context)
This document outlines the process - http://www.htpcguides.com/install-nzbdrone-ubuntu/.
I think it would be great for an official instruction/init.d script that would be used and supported.