On my Void Linux machine I have this on my .bash_profile
if [[ -z $DISPLAY ]] && [[ $(tty) = /dev/tty1 ]]; then
but, you would have to adjust it to your default shell, if not bash, and to adjust the syntax so it works on DragonFlyBSD, the above is for Linux.
Alternatively, you could use nodm, but I have no clue if that has been packaged on DFBSD ?! its available on Void and it doesn't look to difficult to configure.