Even an unidentified noise at midnight can spin into a tale. Hobbies fuel ideas for characters, background and plot. So can careers. Or an author can discover a story in research. Perhaps a historical novelist striking gold in a century old journal kept by a medical student.
Some authors can write an entire book around one antique gown.
Lobsters at the supermarket, a shadow through a shower curtain, even a trip to the zoo have sparked entire novels. Anythiing can set off a writer. Keep notes to stockpile your ideas. Organize your ideas in notebook, on index cards or in a computer. Writers never know when that idea-spark might be needed to light a story bonfire.