Could be a list of reasons. To start, check your ram. To do that go to the search bar on the bottom, (windows 11, should be near windows icon). Type in ram, the first result titled view ram should allow you to that. Check if there enough ram for to use. Ideally while the pc is idle, meaning no open apps, the ram usage should be under 30%. If the ram usage is higher look at apps running in background. From there check which apps are causing high ram usage and try to stop it or uninstall said app/s. Viewing the ram page does allow you to check for viruses. Just look through the apps and if one looks unknown try to uninstall. Hope this helps!