I don't think it is anxiety related at all, it's just that the mind is in a constant state of flux and this is normal for everyone. If doing an activity you'll find your mind is always constatantly thinking in the background. Stop and back track on your thoughts and you will see what I mean. Though I do find it strange some of the things the mind picks up. I was playing the guitar the other day and in the back ground I noticed that I was thinking of something that happend when I was a child. During the times when I didn't have this disorder I use to wake up each morning with a song in my head and it related to nothing. It could have been a song I heard like 20+ years ago and for no apparent reason and I'm singing it in the morning.