a natural inclination
propensity - tendency
A ‘propensity’ is a strong instinct or predisposition for something. It implies a natural tendency to do a certain thing rather than something learned and, therefore, it can be hard to change a propensity one has. As the word is more commonly used in relation to a person’s bad habit(s), that can oftentimes be an issue.
Alex needs to watch his behaviour. He has an unfortunate propensity to get himself into trouble.
The prisoner was not granted an early release date due to his propensity for violence.
Mary is well-liked and respected by everybody in the office due to her propensity for helping others.