Try these steps for starters:
-Make sure your Mac is on the latest software
-check for any app updates
-check your device storage. Your device can become sluggish if it's running low on disk space.
-check your login items by going to the Apple Logo in the upper left corner, click on system settings, then click on general/ log in items. Having too many login items or items running in the background can cause your Mac to take to long to boot up, and things running in the background can slow things down considerably.
-Browsers can be a source of poor performance. Too many extensions and plugins negatively affect your browser's responsiveness. Check each of your browsers extension and test without them installed to see if that's the source of the problem.
-Older version apps might perform worse on newer macOS systems because they lack optimization. Avoid using Java-based apps that require the Java Runtime Environment, as it can tax the performance of your machine.
-Avoid overstressing the CPU or GPU unnecessarily. If you're rendering a video, go make a cup of coffee until it's done.
-Too many tabs open in your browser can significantly reduce performance.
-If you are working online, it could be your wifi causing the slow performance.
Have you noticed using a specific app or program causes the Mac to slow down?
Do you have any third party accessories plugged into your Mac? If so, unplug everything and test each one on its own to see if it may be the culprit.
Try testing in safe mode. Safe mode is a wonderful tool that helps isolate an issue. Going into safe mode alone can sometimes fix issues. Please use this article: Start up your Mac in safe mode - Apple Support
I would also create a test user and see if the Mac is slow in the test user account. If so, then it could be your macOS software causing the issue. See this article: Add a user or group on Mac - Apple Support
If you can isolate it to the software, make sure you have a recent Time Machine backup using an external hard drive, and reinstall your macOS: How to reinstall macOS - Apple Support
See this article: If your Mac runs slowly - Apple Support