This is a bit like one of my personal focus hacks. When I'm struggling, especially in the morning, I'll often set a five minute timer, and tell myself: "surely you can focus on something for five minutes." This is usually enough to get me over the hump, and in the mood to actually get stuff done.
I do think there's something that happens after a short period of intentional focus, where you cross a "barrier" into a state of mind that is more conducive to long-term focus. But there's definitely sometimes real resistance to crossing that barrier.
The problem with pomodoro is eventually you learn that its a trick just to get you started, so your brain eventually goes back to just wanted to never start again.
No technique works without enough genuine desire and motivation to accomplish whatever it is you're aiming to accomplish. (And the belief that you actually have a chance of accomplishing it.) If things like Pomodoro or similar aren't working, then the next step is to figure out if you believe in the path you're on, and are motivated enough to continue on it.
I do think there's something that happens after a short period of intentional focus, where you cross a "barrier" into a state of mind that is more conducive to long-term focus. But there's definitely sometimes real resistance to crossing that barrier.