It might be fungus flies/gnats. They spawn...yes I say spawn because they come out of nowhere! from potted plants that form fungus when they've been overwatered or brought in from outside. Check any potted plants you may have. It's apparent when they come from them. Moving the plant's leaves around and looking at the soil, you'll see a tiny swarm.
Take the plant outside or use an antifungal spray on it. Once the gnats don't have food anymore, they die.