I used to get what we in the upstate ny area called "sweat bug" bites. Whether that's a real bug or not - have NO idea. But it has a tendancy to happen if you sleep in one position and sweat heavily at night - especially in summer. It can feel like something is biting you and can become a rash over time.

If you haven't been having problems with being too hot at night, it could be a nerve thing too. If it's driving you batty, you probably should give your doc a call.