Diagnosis
Yeah, this one's common. The most likely culprit is something—usually a hair—wrapped around the impeller (the fan) inside the handle, throwing it off balance. A less common but possible cause is a failing motor bearing.
How to Fix It
Unplug it. Remove the filter as described above. Use a bright flashlight and look into the filter opening. You should see the silver impeller. Use a pair of tweezers or long-nose pliers to VERY GENTLY pull out any visible hair or debris wrapped around the central spindle. Rotate the impeller slightly by hand to check all sides. Reassemble and test.
If That Didn't Work
If the noise persists and is clearly a metallic grinding, the digital motor's bearings may be failing. There's no user fix for this. You'll need to contact Dyson support for a diagnosis and likely a motor replacement.
Heads Up
Be insanely careful not to bend or scratch the impeller blades with your tools. Even a small dent can cause a permanent vibration and noise.