By default xbindkeys does not start on reboot and therefore can be added to the startup process if required.
xbindkeys needs to be started to work.
xbindkeys
NOTE: This can be used when testing.
Edit ~/.xinitrc and add:
xbindkeys &
NOTE: The & means it will start in the background and the rest of the script will continue to run.
#!/bin/bash xbindkeys &