I have this on every new car I have owned. All modern cars come with knock sensors that are able to adjust timing based on what is needed at the time for more power or better fuel economy. When the car is turned off, the valves are set at a different adjustment than what is needed at start up so it just takes a second for the knock sensor to detect that and make the valve adjustment for a cold start. It is 100% normal and cars that have variable valve timing will all do it upon start up.
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View my fuel log 2015 Mirage ES 1.2 automatic: 42.5 mpg (US) ... 18.1 km/L ... 5.5 L/100 km ... 51.1 mpg (Imp)