The Norton VPN product does not behave the same as the Norton 360 product. For whatever reason, Norton has decided that the Norton VPN interface should display at system startup. There is no setting I have found to change this behaviour.
bjm-'s instructions regarding stopping Norton processes is spot on about having to turn off the Norton Product Tamper Protection before trying to disable a Norton process. But be aware that the Norton VPN product also has real time malware protection and disabling the processes will disable that, not just the interface. Best to just close the interface after you restart your Norton VPN.