What's your passion, as a unique and individual human being, if you could be or do anything what would it be? What would please or entertain you? Think of themes or inspirations from games/books or movies, and convert it to something practical if you have to.
If you had time/resources for any hobby what would it be? What problems might you encounter or others have encountered.
What pings your desire, exscluding the obvious? What makes you curious want to find out more, what do you dream of?
Dont worry if its possible for you are not right now. Make a list of 20 items. Now consider the problems you might enoucter obtaining/doing this thing.
Reserch it and solve one, via product or info. If you enjoy the reserch thats always a good sign. Now do the market research and narow done your list, find your product or create it.