I can offer some possible explanations for why someone, including a therapist, might bite their nails:
Stress or Anxiety: Nail-biting can be a common nervous habit, and therapists, like anyone else, can experience stress or anxiety in their personal or professional lives.
Coping Mechanism: People sometimes engage in repetitive behaviors like nail-biting as a way to cope with stress or other emotional discomfort.
Unconscious Habit: Nail-biting can become an unconscious habit that a person may not even be aware of doing.
Modeling Behavior: Sometimes, individuals can pick up habits from others, either knowingly or unknowingly. If someone they know or work with also bites their nails, they might unconsciously mimic the behavior.
Focus or Concentration: In certain situations, people might bite their nails when they are deep in thought or trying to concentrate on something.
It's essential to remember that therapists are human too, and they can have their struggles and habits like anyone else. If you feel comfortable and the situation is appropriate, you could consider gently bringing it up during a session if it's bothering you or affecting your ability to open up and share. However, if it's not causing any significant issues in your therapy or if it feels too awkward to address, you don't necessarily have to mention it.