You'll need a looping trigger to constantly cause a camera shake near the unit.
To use the Is Unit Moving system, you need both a start (UnitMovingEvent becomes Equal to 1.00) and a stop (UnitMovingEvent becomes Equal to 2) trigger.
On start:
Add UDexUnits[UDex] to a unit group
On stop:
Remove UDexUnits[UDex] from that unit group
Every second (or less):
Pick every unit in your unit group, set RCSS_EventLocation to the position of picked unit and run the camera shake system
You don't need to manually set UDexUnits[], the Unit Indexer trigger does this for you automatically.
On move trigger:
Event is fine
Condition: UDexUnits[UDex] == Molten Giant
Unit Group - Add Molten Giant to Molteno
(do the same for on stop trigger)
In the Run Shake trigger, use position of (Picked unit)