“There is nothing to writing. All you do is sit down at a typewriter and bleed.”
― Ernest Hemingway
I haven't done much 'bleeding' since I started writing, but starting a book can be painful. Inspiration comes from God knows where, but it will, and does come.
The key for getting started for me, was to stick to the old truths - Write about what you know - For me, this was the single most important thing. Basing the main action of the story in Cardiff, and the WW1 action around battle sites I'd visited, were massive positives.
Writing a 'series' of books has helped writing my 2nd and 3rd novels with the continuity of the characters, and plots.
My final tip is to just listen & look. It's amazing what goes on around you which can be included in your stories. Even listening to my sister-in-law has given me the basis for a new character.
Stick with it.