Have you dried deleting the song? Go to file manager, then press Music. This willbring up all the files, find the song and either delete it or move it to another location (a computer or a cloud hosting service like Google Drive or Mega) Make sure it is off that device.
Your batery may not be providing enough voltage. Try plugging it into a wall charger, with the battery out. Does it do the same? Edit: I dont see the restart happening.
But the memory card could actually be full! Try transferring the files to a computer. See if that helps. And if you dont have access to one, then use another memory card.
Try opening it, and fill it with rice to completely dry it. After 24 hours, take the rice out and look at a teardown to see if your device is wired improperly. Update 2/2/17: Actually not rice just dry it with a hair dryer but DO NOT microwave as that is dumb and stupid. Update 3/2/17: Apperantly rice isnt the way to go, use Isopho whatever alcohol to clean the inside and remove corrosion.
