What I can reccomend is:
Check the fuel cap. Specifically the gasket around the filler cap.
Check the fuel lines underhood. (Most likely not as you would likely have a performance issue)
Pull up on the rear seat cushion. It will come out and is held in at the front by two clips. Under it you will see the fuel pump. This location should be dry.
With the cushion removed, turn the key a few times to "ON" but do not start. You will hear the fuel pump kick in and prime the fuel lines. Do this several times and look under the vehicle and under the hood again for wet spots. Placing cardboard under the car along where the fuel line is can help to pick up these spots.
Is the smell continuous, after starting or just in that spot where you started it. Like if you drive for a bit, then stop at a light do you smell it again or just during start up?
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View my fuel log 2015 Micra S automatic: 7.9 L/100 km ... 35.7 mpg (Imp) ... 12.6 km/L ... 29.7 mpg (US) ...