Sometimes it helps to imagine a BIG story moment first.  For example:

A LIFE-THREATENING CHASE

A CALL TO ARMS
(which is a speech that calls characters to action and confrontation!)

A BETRAYAL

Such scenes (and there are many kinds of dramatic scenes) immediately help to define the story and its characters.

Such a scene could come in the middle of the story, or at the end.  We don’t need to write stories from beginning to end, perfectly in order, we just need to get them started!  The right order for the story can be decided later.

New idea:  Consider starting story work with an intense moment of conflict or chaos.  Get arrows flying or a fist pounding on a lectern the second you sit down to write!