Is this Ataxia.

Hi to all, I went for a gym assesment yesterday afternoon i was sat in Alisons Office chatting she asked me to sign some paperwork n i got up to do so but when i tried to sit down i got vertigo missed the chair n nearly ended up on floor the same thing happened again today when i went in with hubby to hosp appointment i went to sit down again missed the chair two days running really what could this be. Dolphin500.