I never feel it's a problem to get ideas. It's more a problem to stop getting ideas
Like when I'm working on a game, I easily get 50 new game ideas. Not all of them are good, but they usually distract me from the game I'm working on.

If you're having trouble coming up with an idea, why not just take an old game and build on it. For example take pacman and see what you can do with it. Perhaps make him collect weapons instead of cherries so he can shoot ghosts. Make a bomb so he can blow a hole in the wall so he can escape the ghosts.
Take an old classic and evolve it is my suggestion if you can't find something to do yourself.