If an intention action is enabled, the alert shows automatically, when the caret rests on the problem-causing piece of code. You can disable alert for any type of intention actions, and show it by explicit invocation only.
Disabled intention actions are marked with the grey light bulb icon . Though disabled, such actions are still available and can be applied to the source code.
You can suppress intention actions related to inspections "on-the-fly", as described in the section Suppressing Inspections.