Robbiee - you are far less likely to encounter it in a skidded helicopter unless you have a gross imbalance on the rotor.
Designers avoid matching the frequencies of the rotors with the resonant frequencies of the airframe.
Helicopters with wheels can be more prone to it as there are more components (tyres, oleos etc) that can wear differently and change their resonant frequency.
More blades also introduce more areas where imbalances can occur.
I had a touch of likely GR in a well maintained H300. Landed in front of a fuel bowser on a very hot day on a newly laid bitumen pad. As I were running down the skids settled into the soft bitumen and became a fixed point for vibration to work against. Took some getting out.