Mac very slow on start up and app initialisation
2017 iMac.
iMac 21.5″ 4K, macOS 11.0
Question marked as
Welcome!
There is a three-question quiz that can help predict if a slow, under-spec factory hard drive is the issue. Three "yes" answers confirm, and you've already answered "yes" to two of them. The third:
"Once launched, do apps seen to run at normal speed?"
From 2012 through 2019, Apple used a slow, laptop-class SATA 3G mechanical hard drive in 2.5-inch iMacs. That drive, even when healthy, ran about 30 percent SLOWER than the desktop-class mech drives they used in entry-level 2011 21.5-inch iMacs. So history teaches that is the likely issue.
However, that is an assumption based on history and not hard data from your computer. We can give you a data-backed evaluation of what's happening and make action recommendations specific to your device if you post a system configuration report. Fortunately there is a safe, secure way to do that without our playing a protracted game of "20 Questions" that could go on for days.
We can quickly and within the confines of these forums help you determine what issues are at play if you use EtreCheck Pro, available here:
The free version will do nicely for this purpose, although the app is worthy of our financial support.
We can see hard data about drive performance, software issues, and RAM usage. Etrecheck is the development of a long-serving and trusted contributor here expressly for displaying information in these forums to help us help you by remotely evaluating Mac issues. It will not reveal any personal or secure information.
Please see this excellent user tip on how to post long text reports like EtreCheck's into a forum response:
How to use the Add Text Feature When Post… - Apple Community