Welcome to the Apple Support Communities. One thing to check on the repeat song is not turned on. The following was taken from the iPod Nano User Guide.
Controlling playback with song controls
The album artwork for the song that’s playing appears on the Now Playing screen. Tap the screen once to show the song controls, and then swipe left to see additional controls and song lyrics (if you added them in iTunes).
Just keep going untill you get to the controls screen.
After that make sure the repeat is not hilighted blue.