Latecomer;
Enstroms have almost 7 sec to get that lever down when entering autoratation due to the fact that it has a HIGH Inertia rotor system unlike the R22.
Most lighter turbines have high inertia systems as well so you have more time to react.
It IS possible to have an engine failure without warning, the governor on a 22 will also mask engine icing so check that carb heat gauge, there is always a chance of losing the drive belts which gives no warning at all until you hear the bang. Its not just for an engine failure you may need to autorotate for.
I would suggest you try and attend a Robinson safety course, that way you will have more knowledge and understanding of the aircraft you fly rather than being afraid of it