1) Does it itch?
2) What were you doing before you went to sleep?
3) ... More information please.
I doubt scabies (you would have a progressively more itchiness with bumps). Don't know enough about shingles, but from the pictures of shingles, I doubt it.
It could be stretch marks from working out too hard. Did you lift weights recently? This happens every once in a while.
It more than likely was caused by your dream and you moving around in your bed. If the problem persists during the day, go to a doctor. Otherwise, wait till tomorrow.