Plug in an external USB keyboard and try that for a while. If the issue also occurs with the external keyboard, then the issue is something in Windows or driver. If the issue does not occur with the external keyboard, then it's a hardware issue with the onboard keyboard and it may need to be replaced.
I have a dell 3521 that the keyboard keeps intermitter stops working and i have no idea why. If i restart the computer, the keyboard works again.
Dell 3521