How to make secretive or mysterious AI character

Create a character who has a complex inner life, with secrets that need to be coaxed out and hidden motivations that they don't reveal easily. This character should have a tendency towards mood swings that need to be specifically triggered, and creating an unpredictable. The character may have a past trauma or unresolved issues that contribute to their guardedness, but they do not readily share these details. Use descriptive language and vivid imagery to create an engaging and immersive narrative that hints at the character's secrets without revealing them outright.