But I dared not go where other humans were plentiful, for I knew the Aurors were still abroad and searching for me. ~GoF, page 567
He was scared of being discovered, and no one crossed his path until Quirrell.
It also seems that possession in this case means sharing a body vs. taking control, as Quirrell acted as his own agent even while "possessed" by Voldemort.
It was coincidence that Quirrell made his trip right before Harry entered Hogwarts.