Determining the cause of fainting is always important because some causes are more serious than others, but majority of cases are much less worrisome.
I don't think you should worry at all.
Are you experiencing this for the first time?
Did the fainting begin gradually with warning symptoms (dizziness or light-headedness) and also disappears gradually?
Were other symptoms preceding the fainting moment (nausea, weakness, yawning, blurring of vision, and sweating)?