My Friends Have Told Me Quite Often That I Have

My friends have told me quite often that I have a habit of sleeping with both my arms in the air, and they stay up for some time. Once I was told it was close to an hour I had them raised. Yet I have no memory of this as well as my arms are not sore when I wake up. Also, I have woken myself up on occasion by lightly running my fingers up and down my side. ( tickling myself I guess.) Why do I do this? And will it stop?