I'm a writer too. Not as a profession, but published. There is a great book by a neurologist on writing called The Midnight Disease: The Drive to Write, Writer's Block, and the Creative Brain by Alice Flaherty. She doesn't write like a scientist; it's very readable.

I used to experience this and once in a while do. I'm currently in grad school again, which requires a fair amount of writing. I basically know that it is more painful to put it off and get all tied up in knots about it so I just jump in and end up losing myself in the process so I don't get stuck.

But there are exceptions. They tend to be when I'm trying to be too ambitious or say too much. That or I am just not truly interested enough but won't admit that. When those things happen, it produces a lot of anxiety which is prolonged by putting it off. If really bad I have to take a sedative, and a little break, have a talk with myself and then try to get back on track.

For me, the best approach is the just jumping in. But when I do get stuck, I try to probe what is really going on underneath and see if I can deal with that to get moving.