Was just wondering whether anyone else experiences this?

Over the past few days I've been finding scratches on my body - two on my chest, one on my upper arm and one on my back. They're not deep enough for any blood to have been drawn, but all the same I'm sure I'd notice if I'd scratched myself, so my only theory is that I've been doing it while asleep? It is a bit odd, though - they don't look like the marks that fingernails would make (sorry, bit graphic!). Just individual scratches.