ECM motor behavior

Is anyone here super familiar with the ECM indoor blower motors? Mine is doing something weird. I understand it will vary its own speed based on certain parameters but how about if it does so sporadically and quickly. For example it’ll be running at say 100% then randomly slow to say 70% then back to 100% all within 1-3 seconds. It also does the opposite with increases of speed too from 100% - 120% and back, also in just a few seconds. These percentages are made up - I’m just trying to illustrate it as best I can. These variations in speed happen every cycle (im fairly sure) I’d say 2-3 times per cycle.