Windows Search (Cortana) is quite a drag, then scheduled disk defrag and sharing Windows Updates.
When the lagging starts, you should check ASAP, what process is causing high disk activity.
You should also check, what tasks are running. Start - Run - taskschd.msc - Display all running tasks.
Hey Auskart, I'm sure you have checked your AV. Its possible too that you may have an infection. Run Malwarebytes. If you cant pinpoint the high usage, you might want to do a repair install. Try going thru running tasks first as Tairku suggests
Here's the link for the repair, choose to keep everything.
Repair Install Windows 10 with an In-place Upgrade
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