I "kinda-sorta" get that too. I don't know if this is the same thing, but I will get something stuck in my head and it's like a like a record that gets stuck on the same spot. Or I just cannot seem to get a phrase I heard on TV out of my head. For me, I think it's anxiety. During the day, if I'm home alone, I turn the tv on or have something going to listen to. At night, I have started bringing my iPhone to bed and listen to a good sleep meditation video I found. It's just a short 10 minute one but it helps me shut my brain off and to fall asleep.