In Chapter Thirty-One, Boo Radley is characterized as uncertain and timid.
When Boo Radley shuffled to his feet, light from the livingroom windows glistened on his forehead. Every move he made was uncertain, as if he were not
sure his hands and feet could make proper contact with the things he touched.
Dr. Reynolds had made a tent-like arrangement over Jem’s arm, to keep the cover off, I guess, and Boo leaned forward and looked over it. An expression of timid
curiosity was on his face, as though he had never seen a boy before. His mouth was slightly open, and he looked at Jem from head to foot. Boo’s hand came up,
but he let it drop to his side.