Did you start with a fresh Volumio system? If so, did you wait to give the system enough time to expand the file system before you installed the Touch Display plugin?
Did you install other software or modify /boot/config.txt or /boot/userconfig.txt? If so, please describe in detail what has been installed / what files have been altered and in what way.
In case of doubt flash Volumio again and start from scratch. This sometimes is faster than analysing the current system.
If you don’t want to do that or if the issue should persist even after installing from scratch, logs would be needed to investigate. For this purpose connect to Volumio via SSH and run
sudo journalctl -f which can be stopped with Ctrl + c any time. You will be able to watch the moment when Volumio begins to restart. Copy the log entries between two Volumio restarts and paste them here or PM me.
BTW: What Pi and what version of Volumio are you using?