Why is Excel suddenly calculating much slower than before?

I've noticed that one of my workbooks has become significantly slower over the past few weeks. It's around 20 MB, contains several PivotTables, XLOOKUP formulas, and conditional formatting.

Simple edits now take a few seconds before Excel responds, even though my PC isn't under heavy load.

Has anyone experienced something similar? Are there any common settings or features that typically cause this kind of slowdown?