1. Startup in Safe Mode: https://support.apple.com/en-us/HT201262
To exit Safe Mode, click in the menu bar and choose “Restart”.
2 If you find your Mac is running slowly, there are a number of potential causes that you can check.
https://support.apple.com/guide/mac-help/if-your-mac-runs-slowly-mchlp1731/mac
3. Repair a storage device in Disk Utility on Mac
https://support.apple.com/guide/disk-utility/repair-a-storage-device-dskutl1040/mac
4. Reset SMC: https://support.apple.com/en-us/HT201295 Choose the appropriate method.
5. If this doesn’t help:
Download EtreCheck, run it to see if there is any adware installed or not.
https://etrecheck.com
Click “Free download” button,
Open Downloads folder, click on it to open, and then select ”Open”.
“Choose a problem” from the popup menu box, and then “Start EtreCheck” in the dialog.
Click “Share Report” button in the toolbar, select “Copy report” .
Paste the report when you reply.
Note: This is a diagnostic test.