I have an example of how to autostart a VirtualBox VM during Windows startup. I’m running Windows 10, but it shouldn’t be much different on Windows Server 2016.
The startup folder on my system is:
C:\Users\chriwill\AppData\Roaming\Microsoft\Windows\Start Menu\Programs\Startup
In that folder I placed a batch file kubuntu.bat with following content:
"C:\Program Files\Oracle\VirtualBox\VBoxManage.exe" startvm kubuntu --type headless
In my example the VM is named kubuntu. You’ll have to change it for your instance.
Addon:
If you need help finding the startup folder on your windows instance press keys Windows + R and enter shell:startup.
Reference: 8.19. VBoxManage startvm