Studies have shown that our brain is optimally creative while it's bored. Long story short, when you're bored your brain doesn't "go to sleep", but rather it makes new connections (aka produces ideas). Some of your best ideas will come when you're in the car, at your in-laws house, or anywhere else you may become bored.
In college, I purposefully started making myself bored immediately before exams by reading the index of the text books. My text scores improved by an average of 10%, by doing nothing else. Quite exciting, to me.
So the next time you're fresh out of ideas, go ahead and do something that will BORE YOU, and stop thinking so hard! The ideas will come