Subtle signs that someone has low self-esteem in bed?

We talk a lot about “bad sex,” but sometimes the time the issue isn’t skills, it’s low self-esteem. You can tell when someone gets into bed and immediately becomes a different version of themselves. They’re suddenly self-conscious, overthinking every move, apologising before anything even happens, or acting like pleasing you is some kind of test they’re scared of failing. What are some signs you've seen?