Yeah, that happens for me too, but it usually takes longer than a few minutes. Probably after about a couple hours is when I lose the energy. I think for me, I will rap over my tracks while I make them (even if it is just gibberish), and i’ll bet that helps keep it fresh. But after some amount of time, I will get very “meh”, especially the next day or the day after.
So recently, to combat this… I’ve either been trying to finish my projects super duper fast, like within 1-2 hours… or if I don’t finish it within that time, I will bounce all the files out to a “save for later” folder, and I’ll come back to it after I’ve long forgotten about the project and when I open it again it will feel fresh.
This is only something I do when making beats though. For my mixing projects, I just bear through it because it requires a lot less creative energy than composing/making music from scratch.