I read on a blog somewhere that the best cure for writer’s block is reading. When you run out of your own material, read someone else’s.
Just like you can imagine a whole puzzle from just one piece, read a small sample of someone else’s puzzle and build out your own from that one piece. And if one piece isn’t enough, read another piece and another, until you start to fill in the rest of the puzzle on your own.
My friend told me about an interview with Aziz Ansari where they asked him, “When’s your next show coming out?” Aziz said something like (paraphrasing), “I have to go out and live more to get more material.”
It’s really hard to sit in your armchair and think up new material from scratch. It’s better if you have a book to read while you’re sitting in the armchair. But it’s best get up and go outside to live as much as you can and get your material that way (especially if you’re a fiction writer or a stand-up comedian).
If you write philosophy or anything more esoteric, might be best to stay in the armchair with a book, because there are fewer people out walking around who are likely to have that sort of information. But then again, Newton thought up gravity sitting under an apple tree.
So maybe start with a book. And if that doesn’t work, get up and go outside.