My ideas come from a mixture of invention and personal experiences (though I should add now my mother never told me she was a fairy godmother who defected to Earth for love! That was pure invention!).
What I have read over the years, news items (and wondering sometimes how things worked out for the people involved when the media have long lost interest in the story) and my interest in British history have all started ideas, which I have then brought together to form characters, clashes those characters would find themselves in because of their natures and so stories are born.
I don't write character biographies (though I understand the point of them) but I do jot down ideas based on themes etc as described above and then worked out "What if?" scenarios. I think it important to recognize that ideas need development time. Yes, a brilliant idea can occur and you write away but in my experience at least it has been ideas coming together to form a powerful whole that has inspired my novels and short stories. The advantage of this is that the ideas are layered and means I am building in depth to my stories.
But it is theme and character types that interest me the most and I like to set characters "going" at one another. Their cause has to be powerful enough though and motivation fascinates me too. Again looking at the news you can pick up thoughts as to what motivated someone to do this or that and then apply that motivation to your characters.