Aerospatiale (now Eurocopter) claims (or did) that the AS350 cannot experience ground resonance. It can, however, experience dynamic divergence. A fart by any other name....
I've had it start many times, and lifting to a hover stops it immediately, assuming the throttle is full open and Nr is sufficient. I once had one go into dynamic divergence after landing. Everything was fine until I reduced the throttle to idle, and then it went bonkers. The bystanders (pilots and mechanics) who didn't run and hide said the skids were coming almost a foot off the ground, and the aircraft turned about 45 degrees on the pad. When it started, I had the throttle at idle, and I wasn't about to try to bring the rpm back up, so I put the throttle in cutoff and pulled the rotor brake full on. It only took a few seconds to stop the movement, and there was no further damage. The inspection revealed only a slight amount of wear in the spherical bearings, nothing else. The springs on the heels of the AS350 can be a real problem, especially on wavy concrete. I don't know if that was the problem, but I've had dynamic divergence start many times on concrete pads in the marsh. I always waited a few seconds after landing before retarding the throttle, and that almost always was sufficient to prevent bouncing, but not that time.