As a person with a surfeit of ideas, and no ambition to write a book (funny how the world works, eh?) I suggest that you start broadly, with the kind of story you want to write:
Crime, romance, sci-fi, fantasy?
Try to explain to yourself what you like about that kind of story. And, what you don't.
Maybe something would have been better with a different character, or such-and-such an aspect of the plot has been done to death? Here's your chance to fix it?
If you don't want to use another book or movie for inspiration, go with reality: carefully changed stories you've heard from other people, or seen/read on the news. (The less you know about the actual story, the better).
Look for ideas that catch your imagination, and toss them around a little.
Off the top of my head:
Example: there have been a lot of stories in the news lately about multi-car accidents.
So, your MC is a paramedic who treats a victim who survives, but is kept sedated until X improves. The paramedic falls in love with their image of the victim, laying there, so peaceful and still, in that hospital bed.
Then, the victim wakes up and is no longer peaceful and sweet: they're a criminal, on the lam, and furious that their loot/retirement fund is missing, and insists that the paramedic immediately search it out, or else.
Or, the victim is a terrorist, who deliberately caused the crash, and is indignant that the mission wasn't as 'successful' as they anticipated, and their life was saved! Insists, perhaps, that the paramedic carry out their mission! Again, or else.
(Note that the descriptions are gender-neutral.)
Ideas are everywhere, and cheap. Let me know what you want, I'll send you some spares.