I've been having a few ideas in the past few months but all failed and now it's just frustrating. I try to relax and think, or work and try and see if anything comes "by accident", but usually the ideas I come up with fall out. One of my main weaknesses is I absolutely cannot write "normal novels". I don't have any examples, so I'll take something Lemex was working on not too long ago: people discovering themselves on a gap year in Greece. I absolutely can't do anything like that, I usually go with fantasy or sci-fi, or something with a specific, strong theme, and more importantly lee-way to invent and create. All my ideas have either been too long, contradictory to the theme, or just impossible to make events around (one was about a man who is assassinated, and is reborn as a detective, and he investigates his death 20 years later. I've never really wanted to write a detective novel and could not come up with anything that could happen to the protagonist, or even really a proper antagonist).
If you don't write normal novels, I would suggest reading more unusual novels. Find books in your style and read more of those. Maybe something like this could help you start out? https://en.wikipedia.org/wiki/Occult_detective_fiction
This has great Blade runner noirish possibilities. Not sure what the problem is though. Ideas aren't stories you have to follow through each component of a novel - even if it's not on paper, it could just be in your imagination - and start filling in the blanks. Like for instance take this idea does the mc know he's reborn or is it just luck that he's investigating his own death? Is he a P.I. hired by someone or a police detective? Was his life better in the past. Was he a prominent figure or a bad guy ( mafia, mob, crooked politician, )? Who wanted him dead - maybe the antagonist is actually a good guy? Does anyone else know he has been reborn and are they trying to stop his investigation? Is the rebirth process ' simple reincarnation' or something more sci-fi complicated? Does it take place in grimy back alleys and gambling joints or sunny California beach houses or maybe some future landscape? What's his motivation to investigate? What was the antagonist's motivation to kill him? The more questions you can ask and answer the more you can start shaping scenes & happenings. You don't need a big theme either - the theme could be something simple like redemption... if he was a bad guy in the past, he's got a chance to right some wrongs. Or maybe identity - the mc is forever trying to figure out who he is.
Oh God, please not "people discovering themselves" while travelling. I have travelled extensively- I have never "discovered myself", I never lost myself in the first place- however, I did have a bloody good holiday.
That's exactly why it didn't go anywhere. It was really just an attempt to commit some funny stories and some experiences to paper and it just didn't work as a short story.
Yeah, some of these I don't know if I get. I've read a few and a lot just felt like vignettes - I didn't get any strong feeling that anyone 'found' themselves. Just maybe reinforced who they were in the first place. Though I've felt like writing a short story based on an idea that happened with my mother. We traveled with her back to her hometown hoping to find some childhood pictures of her because her house burned down when she was young destroying everything. The earliest picture she had of herself was when she moved to my hometown when she was fourteen. She met up with relatives, old friends, strangers - who might've known her mother - in her quest.
Not really sure what you're asking for. Do you want suggestions about the plot you've told us about? I don't think I could improve on @peachalulu 's suggestions. Or something like a recommendation for a book you could read about plots? Like 20 Master Plots: And How To Build Them, by Ronald B Tobias?
I don't think many could improve on @peachalulu's excellent post. Finding the right plot you want to work with can take time - I remember reading somewhere than when she came up with the idea for Potter it was after months of search, and she felt an all-over shiver of pleasure as if to think 'Yes, that is exactly it!'
You know what... Try using some ideas from dreams you've had and fit them together in a way that it matches...
As Peachalulu says, this is an excellent idea. Only issue that I can see is that, even if he is reborn at the moment of his death, a 20-year old detective would be very junior...possibly, his death is a case study at police academy - and he comes across evidence (helped by flashbacks into his former life) that blow the original "culprit" wide open...perhaps his rebirth is to the wife of the guy who was originally convicted? Now there, I took a problem, and free-associated it to a couple more possibilities. I even impressed myself! As far as "never wanted to write a XXXX novel"...you could write it as a love story, sci-fi, fantasy, comedy, whatever. The crime and solution aspect need only be enough to deal with that aspect. Or you may find that you love it. As far as "not coming up with anything that could happen"...just start writing and see where it takes you. Maybe you're right. You may be one of those people who can't think of what to write. That's what us writers call normal people.