I never have an issue with this at work. Clients give us specifications, so deciding what I need to solve is never a problem. I definitely have this issue on personal projects though. It's often because I'm still trying to figure out the problem space.
I agree with nsxwolf, this is more of a designer's block than coder's block.
I agree with nsxwolf, this is more of a designer's block than coder's block.