Yes moods happen for no reason. try tracking them though- write down the time of day/drugs/caffiene/sleep etc. you might find a pattern. i'm always depressed in the morning until i do something.

Sometimes self-harming thoughts come with increased energy. I used to want to hurt myself but didnt have the energy, then i would get the energy and actaully do it. this went on for years before my dx. now that i'm "stable" on meds, just having energy triggers thoughts of self harm. I just acknowledge them and let them go.