Your service is starting, as is evident from the logged message "Started My Shell Script."

It's odd that you're using sudo in the script. The script is already run as root by the service. Also, sudo asks for a password, but you can't give it one because you're not running it from the terminal. Xrandr doesn't even need root

I believe the error message is happening because xrandr needs the DISPLAY environment variable, which is inherited by applications launched from the desktop (e.g. by the "startup applications" feature of your desktop environment, from .xinitrc, or when running it from a terminal window)

See https://wiki.archlinux.org/title/Xrandr#Configuration_using_arandr for something you could try

Instead of a script try the command directly in ExecStart. Systemd should take care of keeping the process running without you having to do nohop and disown.

If you insist on using a script you should use a full path to sh or bash with the path to your script as an argument like ExecStart=/usr/bin/bash /path/to/script.sh.

Your xrandr script is missing output monitor. Try this

COMMAND=/usr/bin/xrandr --ouput LVDS1 --rotate normal

If LVDS1 is incorrect. You can check the output by running xrandr.

https://wiki.archlinux.org/title/Xrandr#Scripts