My laptop is suddenly much slower, how do I find the error?

My laptop lagged abnormally much since yesterday. Is there a program where I can find the error? Incidentally, I haven't installed anything for a long time

Maybe you should clean out the startup folder.

Use the system backup to reset to a date before it got slow, otherwise only reinstalling or resetting usually helps.

Where can you find it?

You can simply download autoruns that will show you everything in autostart from the regestry to normal things like the task manager