start-vm@.service

[Unit]
Description = Virtualbox VM
After = systemd-user-sessions.service network.target sound.target
ConditionPathExists = /dev/tty0

[Service]
Type = simple
TTYPath = /dev/tty8
StandardInput = tty
StandardOutput = tty
# Reset the terminal device specified with TTYPath= 
# before and after execution. 
TTYReset = yes
TTYVHangup = yes
# clear the screeen
TTYVTDisallocate=yes

PermissionsStartOnly = true

User = < YOU USER >
Group = vboxusers

PAMName = login

ExecStart = /usr/bin/xinit /usr/bin/dbus-launch --exit-with-session \
  /usr/lib/virtualbox/VirtualBox --startvm "%i" --fullscreen --no-startvm-errormsgbox -- \
  :1 -nolisten tcp vt8

ExecStop = /usr/bin/VBoxManage controlvm "%i" poweroff

Restart = on-abort
RestartSec = 5
SyslogIdentifier = virtualbox-%i

[Install]
WantedBy = multi-user.target