When trying to figure out what to code or how to solve a problem, pen and paper is too "concrete" for me for some reason. If I'm waiting for inspiration I would rather just go for a walk or pace back and forth or just stare at something (monitor, wall, whatever) and think it through. When I write something down (or especially when I type it into a document) it becomes too set in stone for me, and if I do it too much I get way too "close" to it to see the solution.
Pen and paper is more helpful when I'm trying to see how the solution I came up with fits into the code, at least for me. I can't visualize at all, so even basic things about how data flows will be helpful if I write them down. The more concrete I'm getting, the more I use pen and paper or text documents. Otherwise it's just give myself time to work through the code as I know it, thinking of things and discarding them quickly, and waiting for inspiration to strike.
Pen and paper is more helpful when I'm trying to see how the solution I came up with fits into the code, at least for me. I can't visualize at all, so even basic things about how data flows will be helpful if I write them down. The more concrete I'm getting, the more I use pen and paper or text documents. Otherwise it's just give myself time to work through the code as I know it, thinking of things and discarding them quickly, and waiting for inspiration to strike.