Which Linux distro do you use? If you use something based on systemd (Debian, Ubuntu) you can run DOSBox with a shellscript like this:

1#!/bin/bash
2dosbox
3systemctl poweroff

Just put this in a text editor in a file called "dosbox.sh" in your home directory. Then do "chmod +x dosbox.sh" in a terminal, and then you can run the script via "./dosbox.sh" in the terminal. Use your favorite search engine on how to put this into an icon on your desktop or whatever you like best...

Alternatively "systemctl suspend" will suspend the machine, if that is more to your taste.