wonder - To feel curiosity or doubt about something; to question or inquire about something, often with a sense of awe or amazement.

When she saw the magician perform his final trick with the glass ball, she couldn't stop wondering how he did the trick.
reticent - Describing someone who is inclined to keep their thoughts, feelings, or personal matters to themselves, not expressing them freely.

He was reticent about discussing his past, thinking that there were details that she might not react well too.