a natural inclination
proclivity - tendency
A ‘proclivity’ is something that you are naturally drawn to or disposed to do, as if automatic rather than a conscious decision. While it can be used to express all kinds of tendencies, it is perhaps more commonly used in relation to something considered morally wrong or objectionable.
Even as a child, Paul displayed a proclivity for aggressive behaviour and violence.
The tell-all book details the sexual proclivities of Hollywood stars.
Lucy has a proclivity for risk-taking, which can be beneficial in her line of work.