Skoda Citigo plastic burning smell on 3 year old car.

It sounds as if it is the DPF trying to regenerate which is perfectly normal . When it does this you get tremendous heat , possibly engine noise and engine fan kicks in until it completes the cycle . With you only doing short journeys it will not be enough time to complete the cycle .What the car needs is a decent run down the motorway at a fair speed to clean out the cobwebs and let the regenerating process complete . This should be done every so often to avoid problems further down the line