My Brain Is Lifting Weights

I am 4 weeks scholar and am trying to break habitual thoughts and actions that always occur when I need to sit down and work towards my business.
The way it works in my case is that as soon as I sit down on my scheduled time to do work my brain ‘directs’ me to lookup makeup tutorial videos, latest trends in fashion, and other Instagram account photos. I comply each time and I get a relief from doing the work. I get to live in roses and daisies and before I know it, four hours have passed.
The last few days I tried to pause as soon as I saw my hand reaching out to open a browser that is not related to my work. I realized that even though I did not HEAR any thought, I got an automatic message that caused me to reach out as I’ve always did and procrastinate.

I shook my head and angrily said, ‘NO! No procrastinating! Work, damn it, work!’ and then the next hour, when I tried to sit down and work, it felt literally like I am asking my brain to lift weights. One hour of demanded focus got my brain exhausted. I yawned tirelessly and almost fell asleep.
Is that normal?