Female 26yo with occasional spinning vertigo attacks lasting <5 sec, usually with head movement both in and out of bed. cause for worry?

Probably BPPV: Benign Paroxysmal Positional Vertigo is usually due to free-floating crystals (otoliths) in the semicircular canals of the inner ear. The best treatments are manipulations to move the stones, either the Epley or Semont maneuvers - usually done by neurologists or ENTs. If the Epley maneuvers help, you can learn to do them at home with DizzyFIX, a device available on Amazon for $140.