A nudge represents a gentle push, intended to help people change behavior in a desirable direction. Personalization and context-awareness make it possible to tailor a nudge to the user’s specific needs and the current situation, and thus make it relevant and meaningful to the user. To be effective, a nudge must be given at a time when the user needs to be pushed and is able to follow the nudge. This paper presents how triggers, based on the event-condition-action (ECA) rule, enable timely nudging by starting the nudge design process at the right time so that a nudge is available when the user is susceptible to nudging. The triggers are tailored to the user’s situation and need for nudging, by personalizing both event detection and the evaluation of the condition for starting the nudge design action.