UP, I definitely have unexplained low moods. Exercise always shifts me back to a more positive state.
I also agree, high energy music can help, especially something that I can try to sing to (but that's probably because my singing just makes me laugh).
I have also been known to tell myself a really corny joke while looking in the mirror then making myself roar with laughter. I know this sounds a bit weird, and do be mindful of the neighbours, but it works for me when I just need to surprise myself with a bit of eccentricity.
Please let us know how you're doing, if it doesn't pass soon, I have some more extreme ideas, but I'm hoping you won't need to stoop to my really bizarre "banish the low mood" strategies.