I not sure what you mean x250 I assume Peugout or another Seval deriviative petrol or diesel ? Two things however spring to mind is the airflow intake set at summer position good old days winter time set the nozzle downwards to avoid the chill ...Fiats Uno and panda use to suffer bad from this it was the jets in the carb freezing at standstill would thaw out ...set off again and the wind chill meant they would freeze and stall ,,,,the prcess repeated heat from the manifold would thaw
It took Fiat ages to work out what was happening and the air filter was not adjustable ....In the end and a clumsy but effective solution behind the grill we used to block it off with plastic to shield the carbs and filter and hey presto no problems there was another solution but I cant remember and this worked.
I suppose even if diesel you could have the same problem diesel can freeze but at injection point more pertinent the effects of waxing more dramatic
I am not saying this is the cause but experience from the past with similar circumstances so unless anyone comes up with a more definitive answer worth considering
Channa