You were abducted by otherworldly beings (planar, fey, fiend or celestial) Moments later, you reappear, but has physically aged 1d10+10 years, has no memories of that lost time, and has not mentally aged even a minute.
Approaching adulthood you experience wanderlust and decide to travel, roll 1d6 to detirmine years spent travelling and think about where your character might have gone. (work with your DM to determine details)