Hello, (Please read full answer before attempting).
Please try plugging the iPod into your Computer and loading up iTunes, A window should then pop up saying that your iPhone is in recovery mode or just that it needs to be restored before you can use it. Proceed to restore the iPhone.
It can take a while so do not be tempted into resetting it during the Restore as this causes the Connect to iTunes page to appear again and is sometimes irreversible with iPhones when the restore is interrupted.
If the restore works then your phone should be back up and running, if not then load up iTunes again and it will say restore unsuccessful and will give you an error code. If the restore did not work please comment the error code and we will go from there :)
Sadly I do not think you can back up the data before hand and the iPhone is failing to start so needs the software reinstalling or hardware replacing.
Please comment your results :)