Eu acho que você provavelmente quer usar a opção --loop
para reiniciar x11vnc
-loop
Create an outer loop restarting the x11vnc process whenever it
terminates. -bg and -inetd are ignored in this mode (however
see -loopbg below).
Useful for continuing even if the X server terminates and
restarts (at that moment the process will need permission to
reconnect to the new X server of course).