I've experienced lag when viewing in the viewport window, selecting objects', and moving selected objects'.
Adding more computer RAM (previously 8gb, now 64gb)
Turning off OpenGL Depth-Picking in the User Preferences
The issues always happens over time, while at first there is no lag, no matter how simple or complex the scene is.
Minus the said RAM upgrade:
OS: Windows 11 Home (15-dy2024nr, Natural silver) Brand: HP 15-inch Laptop CPU: 11th Generation Intel Core i5-1135G7 GPU: Intel Iris Xe Graphics RAM: 8gb (now 64gb) SSD: 256gb
I forgot to mention it's just about everything that slows Blender down when I'm using it. So, again, scene complexity is not a contributing factor to my lag I think.