“Inside the ear is a tiny organ called the vestibular labyrinth. It includes three loop-shaped structures called semicircular canals. They have fluid and fine, hairlike sensors that detect the head’s movement.

Other structures in the ear, called otolith organs, detect the head’s movements up and down, right and left, back and forth. The otolith organs hold crystals that respond to gravity.

For many reasons, these crystals can move out of place. When the crystals move, they can go into one of the semicircular canals. Certain head movements can cause the crystals to move.

When the crystals move, they cause the semicircular canal to become sensitive to certain head position changes. This is what causes the dizziness.”

MAYO CLINIC ( Benign paroxysmal positional vertigo (BPPV) – Symptoms and causes – Mayo Clinic )