Spinning beach ball on every file save or download in brand new M4 Mac Mini

Part 1 of 2

Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal.

Safe Mode will also eliminate Third Party Software, extensions and drivers from loading. It will only load the Minimum amount of Core Apple Processes to allow the the computer to function at a reduced Level of Performance 

Does the issue present in this mode ?

Sometimes a Safe Boot followed by a Normal Boot will just put things right.

If not - there could be something in the main User Account playing up. To further isolate this - Set up users, guests, and groups on Mac. Then log out of the Main User account and log into the dummy account and test again if the issue persists.

If the issue is present in the dummy account - then, this appears to be a System Wide issue on the computer.

Part 2 of 2

To Drill Down further and to avoid a session of Q&A, Q&A  and Q&A  

Download the Application Etrecheck  ( External Link ) directly from the Developer.

The Application is Not a " Silver Bullet "  and is  only a tool to examine the Hardware / Software used on this computer 

This is a Diagnostic Tool that makes no changes to the computer Hardware / Software used on this computer 

The application is free or paid from added features. 

The Report will Not Reveal Any Personal Information. 

Post back the Full Report - copy and paste - >>>> using the Additional Text Icon ( 3rd Icon to last ) <<<<

Do you have an external drive attached which you allow to sleep? When you open or save, macOS polls all connected drives. Sometimes, drives end up mounting using USB2, so the time waiting for the drive to spin up and be ready can be painful.

Please do follow Owl-53's solid advice.

To add a little bit: when this happens, it is almost always the case the use migrated everything from a previous mac, and some of the old stuff is causing a problem in the new machine/OS. This is particularly relevant when the move is from a completely different architecture, as in going from an Intel to an Apple Silicon Mac.

If I were to guess - and, why not? - I'd say you probably have an "antivirus" in there...