BPPV is due to debris, or crystals that collect within the inner part of the ear (canals) that helps with balance. These crystals "interfere" with the balance signals and result in brief spinning with movements such as looking up/down, turning your head and/or rolling over in bed.
Diagnosis of BPPV can usually be made with an appropriate examination consisting of questions relating to your dizziness symptoms, and with some physical tests/movements that cause the crystals to move about in the ear. This unfortunately usually provokes the dizziness but is necessary to be able to diagnose this condition and ensure the cause of your dizziness is not another reason.
Whilst BPPV can get better with time, often treatment by a physiotherapist will help the condition clear up much sooner (research suggests usually within 3 to 4 treatments). The treatment involves certain movements/maneurvres guided by the physiotherapist that "move" the crystals out of the ear canals. Home exercises can also be given to achieve the same results.