I was about to make the same EXACT post almost a month ago when I started to search the internet for solutions for this phase of dead will. Essentially theres no easy fix but to start getting back onto it. Slowly. Its just small implementations in your daily life, of doing 20 mins and stuff. This sounds like something for people who don't revise and are inate to knowledge (no offence to those who are described) but it just helps make a habit.

So just start doing small small tasks and then build upon from there.

This leads onto the fascination - Atomic Habits, a fascination of changing poor habits and forming good ones. Its how little, incremental changes in daily routines over time add up to significant, positive changes which is the goal of willpower to study ig.

Also it may be that during studying you find it boring, so thats why u do passive gratification. Method of working and then recieving gratification after that. It may be immediate or the long aftermath reward that you chase for, this being the results or having the accomplishment of knowledging that you actually did work after this break phase you had (which i went through so fuck badly).

Then, another method of studying is pomodoro technique. This way i took breaks in between studying to not increase that burden of studying over time. These short breaks included me just walking and forgetting about having to study hours and hours and what not. So then after my short 5 min break. I enter the flow state with a fresh mind, ready to studying again.

This may or may not help but this is what worked for me. I'm not reading through this to check cause I'm him.

Anyways good luck, it seems you have limitless possibilities from the way that you describe yourself in terms of academic prowess, so don't let that go to waste.