It happened randomly. No update, no changes to my use. Opened it up at work one day and now experience lag all over the place. I almost always have Figma or InDesign open plit screen, so the most annoying part is now switching between the two. It takes around 5 seconds for the program to start working with every switch. Then ther's problems like the program refusing to let me move objects, clicks not getting registered, etc.
I have tried reinstalling, no luck. I have used Illustrator consistently for a very long time and have never experienced this issue. It is by far my most used used CC app. This should not be happening on a Ryzen 7 5000 series machine.
Without exact system info we can't tell you much from issues with hardware acceleration or other such stuff to the operating system doing weird things and running out of memory this could be anything. The first thing would be to reboot and run a system check. Everything else requires better info.
Sorry to hear about this experience. Is Illustrator behaving this way with all of your files? If yes, kindly try resetting Illustrator's preferences by following the steps shared in this article (https://helpx.adobe.com/illustrator/kb/troubleshoot-preference-issues.html) and sharing your observations. Disclaimer: Please note that resetting preferences will remove all custom settings, and Illustrator will launch with the defaults. You may take a backup of these settings from the location mentioned in the article.