@reboot /home/USER_NAME/TEASPEAKSERVERFOLDERNAME/teastart.sh start
it will do for restart and too boot up.
[Unit]
Description=NAME
After=network.target
[Service]
WorkingDirectory=/path/to/
User=TEASPEAKUSER
Group=TEASPEAKGROUP
Type=forking
ExecStart=/path/to/teastart.sh start
ExecStop=/path/to/teastart.sh stop
PIDFile=/path/to/tpid.pid
RestartSec=10
Restart=always
[Install]
WantedBy=multi-user.target