Have you tried resetting it?
If that doesn’t help, you can also try manually re-installing the firmware. Formatting is the 3rd option. Note that formatting will erase any files (music, sudiobooks, etc.) that you have on it, so you would have to re-transfer those afterwards.
There’s really nothing else you can do. If none of these 3 options work, then I suggest calling/contacting SanDisk about a possible warranty replacement.
