Is a passive protagonist at the start a problem?
A protagonist who will not act at the start is the defense working correctly, and what they have surrendered is their say rather than their energy.
How to write your protagonist's trauma
A protagonist's trauma is the painful event in their past that taught them how to stay safe. What matters most for your story is what it left behind: a habit that protects them, a fear they can name, and a deeper fear they can't.
When the trauma is specific, the rest of your story has something to push against. Your protagonist's reluctance at the start makes sense, your antagonist has a weak spot to aim at, and your ending knows what it has to heal.
Each insight below takes one piece of this at a time, with an example from a film you probably know.