How do you start a short story?
My stories always start with a character. I don't know why they start that way, but they do. Next I give the character a plot problem. A big one. Then I stop developing the story util I can come up with an ending. Once I have an ending , I develop the characters, plots, scenes, setting and all the other details that go into a story. If I can't figure out a good ending, I don't bother working on the story details because the story isn't going anyplace.
Works for me. May not work for other folks.
“Begin at the beginning," the King said, very gravely, "and go on till you come to the end: then stop.”
― Lewis Carroll,
Sometimes I begin at what I think is the beginning, but later it becomes the middle. I may not have a clear idea for an ending, but I just trust that as I write it will come. It usually does, though it may require a bit of tweaking.