Why do I keep having this dream?

In the dream I am in trouble with the police (or sometimes it's the FBI) but I haven't done anything wrong. Sometimes they are hunting for me but I slip away from them and flee. In the dream, I know I haven't broken the law but I am still scared. Sometimes I have been arrested or just taken into custody and I am terrified. The police talk tough to me like I'm a criminal and I am too scared to think straight or know what to do. I wake up feeling sure I will be arrested shortly and that I will be treated so roughly it will kill me. I have to talk myself back into sanity because, in my real life, I live quietly within the law, and I have no reason to fear the police. I don't even get parking tickets!