Working Without Distraction

I am a writer and am writing my very first novel.
I have been working on this story for four years to a certain capacity and kept changing the main story a few times.

I have now decided to give one idea for the story a go till the end and at the very least write an outline of the plot in 4 pages.
When I am scheduled to write I do sit down at my desk, I take a notebook or open the document and give it a couple of minutes.
Then, when no idea comes up, I open a browser to pass the time until an idea will land on my desk.

After doing it for as long as I can remember, I understood this method is not working because clearly my result is that I don’t have a completed plot outline.

When I consider not opening a browser when no idea comes to my mind, my brain comments on that with:
“No one just sits around at their desk waiting for ideas doing nothing.”

When I think this Thought, it creates for me an urge to then open a browser again and there the Model unfolds as before.
So, I know that this Thought above doesn’t serve me well.

When I entertain stay only with my notebook and nothing else (phone and browser closed) I get anxious and restless.
The Model that plays here is:

C = Sitting to write with no distraction, only notebook
T = What if no idea will come to me? / No idea comes to me
F = Restless, Anxious
A = Shaking my legs, making myself another coffee, reading my notes again, worrying, contemplating justifying distracting
R = I get no writing done, I break my protocol promise, I break my no distracting promise, I get no ideas

So, I understand intellectually that my brain doesn’t like sitting down patiently and waiting for ideas and that distracting is far easier and more fun.
How do you suggest I will build up this muscle?
When I block 4-5 hours of writing, to think of sitting like this all these hours and generating nothing seems painful.