[bjoernbu]

For me there is one thing that works so much better than anything else: new goals. To the end of my PhD, that meant to just suckt it up and finish the work despite low motivation and frankly also workweeks far below 40h.

Later in life, motivation came naturally, I worked more and I am really happy with the outcomes. Sorry, that this is no advice that is immediately helpful, but I hope that it can be reassuring that streaks of low motivation as a student are kind of "normal" and not necessarily something that needs complex solutions.

[sheepybloke]

I agree with this! Honestly, I felt a lot of the same emotions op felt the week or two after exams finished or when large projects wrapped up. To me, the sudden drop of going from 100% on and focused on accomplishing a goal to having it all finished was huge impact on my motivation. Finding a new goal helped to bring me back out of that low.