I had it really bad in my second trimester and the doctor told me that I had a good case of vertigo it didn't matter what I did it wouldn't go away by my third trimester it completely disappeared hope this kinda helps you a little bit
My OB warned that this might happen when I stood up, but when you're resting that does seem a little strange. Maybe your blood sugar's a little low? You might try eating a snack every 2-3 hours between meals, see if that helps.
Its not really normal. are you getting enough water? That is a sign that your blood pressure is low. for sure its a reason to go in a see the dr. but make sure someone is driving you there. We don't want you to get into an accident on the way there.