Benign Paroxysmal Positional Vertigo.
  BPPV is the most common type of vertigo.  However, there are other numerous causes and only a doctor can diagnose the cause of your dizzyness.  BPPV is characterized by brief episodes of dizzyness that last 15 to 30 seconds and occur in associoation with rapid changes in head postion (ie standing, looking over your shoulder, rising from putting of shoes etc.).  Click here for a useful link to exercises you can perform at home.