Hello @riddhisiddhi7 , I am not Dell employee, just a computer owner like you.  Without any information given for your computer or version of windows you are using, I am going to suggest that you uninstall the latest update to see if it was the cause.

To do this, go to windows settings, select update & security, select view update history, select uninstall updates, you will see a list of windows updates with installed dates, select the update with the latest date to uninstall.  Reboot and test your pc to see if it fix the issue.

If the issue persists, post back with better info about your pc and software, what tasks were running when lagging.  Do not post any personal information in here.

Chino,