VBoxHeadless
may be what you're after.
Regardless of if you create a new VM or import an old one, you can start it with the command:
VBoxHeadless --startvm "Ubuntu 16.04 Server"
(Replace Ubuntu 16.04 Server with the name of your VM.)
VBoxHeadless will start the VM and a VRDP (VirtualBox Remote Desktop Protocol) server which allows you to see the VM's output remotely on another machine.
To stop a VM, run
VBoxManage controlvm "Ubuntu 16.04 Server" poweroff
To pause a VM, run
VBoxManage controlvm "Ubuntu 16.04 Server" pause
To reset a VM, run
VBoxManage controlvm "Ubuntu 16.04 Server" reset
I've been researching this tonight for another reason, making it a little more flexible to my needs isn't working, but it may be just what you need.
also:
$ VBoxHeadless --help
Oracle VM VirtualBox Headless Interface 5.2.10
(C) 2008-2018 Oracle Corporation
All rights reserved.
Usage:
-s, -startvm, --startvm <name|uuid> Start given VM (required argument)
-v, -vrde, --vrde on|off|config Enable or disable the VRDE server
or don't change the setting (default)
-e, -vrdeproperty, --vrdeproperty <name=[value]> Set a VRDE property:
"TCP/Ports" - comma-separated list of
ports the VRDE server can bind to; dash
between two port numbers specifies range
"TCP/Address" - interface IP the VRDE
server will bind to
--settingspw <pw> Specify the settings password
--settingspwfile <file> Specify a file containing the
settings password
-start-paused, --start-paused Start the VM in paused state
-c, -capture, --capture Record the VM screen output to a file
-w, --width Frame width when recording
-h, --height Frame height when recording
-r, --bitrate Recording bit rate when recording
-f, --filename File name when recording. The codec used
will be chosen based on file extension
note: right before posting I saw this is a few years old. Sorry for dragging up something from the archives, but I do feel it's useful to post.