The spinning wheel in a word document

I am working on a pretty large word document of almost 6000 pages. There was no such problem with my old iMac computer. However, since I bought the new iMac with M1 chip every time I type something or make a correction on the document the spinning wheels goes on and on. I also noticed that the air vents area gets very hot. So I put an outside fan to cool the area. Cool it did, but the wheel comes on and on at most times and is becoming a truly annoying feature. Is this an iMac problem or a WORD problem?