Burnout drains your motivation, but unlike depression, it goes away when you go on vacation and lose the deadlines. Read up on it a bit, and if it sounds like what you're experiencing, do what Google tells you (take a break, focus on intrinsic motivation over extrinsic, align your motivation with your goals, take care of your body, etc.) and it will clear up. It may be that's not the problem, but I'll share some of the ways I overcame it in college because they apply to motivation in general.
1) I reengaged with a friend. I was so busy and stressed that I went months at a time without making social plans, and when a she wanted to get coffee, the first thing through my mind was how taking a few hours off from studying would make me that much more overwhelmed. She told me about burnout, and that's how I realized I was in a temporary state that I could get out of. Beyond that insight, just talking with a friend and breaking my isolation was the right thing to do for my social and mental well-being.
2) I switched from an accomplishment-oriented schedule (I'm done once I finish this task) to a time-based schedule (I have two weeks to do this assignment, and it will take me up to 20 hours, so I'll spend 2 hours on it per work day; that leaves six hours for these other projects, eight hours for sleep, and eight hours of free time.) I made a spreadsheet so I could see how much I was accomplishing and see that I'd have time to finish everything.
This made a big difference. There was always more work to do, always some long term project that wasn't finished yet that I felt like I had to work on, but scheduling time for it made it possible to take free time without worrying I was being lazy and I was never going to finish. It made my work, even huge projects, feel manageable.
3) I reevaluated my motivation. I was motivated by a sense of duty and obligation to work hard and make the most of my education, by grades, and by not wanting to fail. Hearing someone say, "Hard work pays off," was a great reminder to me that there were better reasons for what I was doing. Looking back, my hard work really did pay off. My education prepared me for my current job, which I love going to even on Mondays. It was very encouraging to look forward to the payoff and remind myself that my work was adding up to something.
4) I gave myself a break. I made it through the term by changing my time management and reevaluating my motivation, and the next term, I signed up for a lighter workload. I made it through college, and I've avoided going through burnout again by keeping an eye on my working hours and my motivation.
TL;DR: Take care of yourself, make some progress each day, don't forget your real motivations in the midst of your proxy motivators, take time off when you need it, and know that you're doing a good job and your work will pay off.