Hahaha I'll try to explain it better, but let's use this image as a reference:
(remembering that this is one of the ways we can mix a song, however, to explain to you what I meant, it will be easier to guide us by this model, hahahaha)
Basically, we have two incredible vectors for “positioning” the tracks/stems/lines, which are: Panorama and Reverb.
“PAN” helps to shift the sound to the right, left and/or spread the width of the volume of what we're hearing. Reverberation gives us a sense of the depth positioning of what we're hearing (whether it's closer or further away - remember that I'm talking about “basically”, as there are many other factors such as reflection, type of material, etc.).
So I think you've understood how much we can play with where we want each instrument to be in a way that relates left/right to near/far, where the volume (db) will give us the amount of force to notice.
Returning to the image, now look at how the author positioned the instruments. As well as getting a sense of volume and pan, we can also interpret that the height at which he placed the names of the instruments could also be the distance from the central convergence of the image from near to far.
So, finally, answering your question about your composition (lol): the impression of fluctuation is more to do with the fact that I can't understand if it's on purpose that the instruments don't have a fixed positioning during your music or if it's so that they behave as if they were floating from side to side. That's what I meant: if it's to float, make it more obvious (which makes sense, as they sound like they're being played by ghost musicians hahahahah).
(sorry for my English, I'm Brazilian)