Do you have any diagnostic codes? Is the check engine light on? Have you tried holding the gas pedal all the way to the floor when cold-starting?
Not familiar w/that make/model, don’t think they are sold here in the USA. But that won’t stop me from answering (i.e. guessing about) your question … lol … I presume this is a gasoline engine. The aroma of gasoline may be normal if only noticed a short time period, and only after a cold start. Gasoline engines require a very rich mixture when starting cold, and some of that gas remains unburned and comes out the tailpipe, hence the odor. Both my Corolla and truck produce a mild gasoline odor on cold starts, lasts maybe 30 seconds.
I’m also presuming the engine starts right up fine when it is warm, and also idles perfectly when warm, and when the engine is warm, no balking when moving from a stop sign. hmmmm … my guess is there’s something wrong with the cold start system. It varies car to car, but on most 2012’s the way that works is the engine computer reads the coolant and ambient temperature sensors, and from that determines how much gasoline to inject during the cranking phase. The colder either of them reads, the more gasoline injected. If it reads really cold the computer will double pulse the injectors. Use your scan tool to verify those two sensors are reading correctly. If you don’t have a scan tool, at least check those two sensors are properly connected to the wiring harness. If the connector comes loose the computer may think it is 40 deg F below zero, and will really inject a lot of gasoline, which could explain the symptoms.
Your battery measurements are good, so that’s unlikely the problem. However, besides injecting extra gas the computer may raise the spark plug voltages on cold starts, and if that isn’t happening, that could explain it. Much less likely than the above theory though.
A vacuum leak could explain it too, as it would cause the mixture to be too lean for cold starting. The problem w/this theory is that a vacuum leak that severe would usually show up as symptoms during warm idle. And it would probably produce a “too lean” diagnostic code.