http://www.pneuro.com/publications/dizzy/

Test your BP both in standing and laying down positions.​

Check for: orthostatic hypotension

Try: Epley maneuver http://www.dizziness-and-balance.com/disorders/bppv/bppv.html
http://www.dizziness-and-balance.com/disorders/bppv/epley/first.html