It won't; EVs don't have volatile gasoline inside them, so why would they ever burn? Just ask Tesla.
Satire aside, we have precious little information on this vehicle. Mercedes has a separate brand for its electric cars, kicking off with the EQC crossover. The promise of bespoke platforms is there, but with sales numbers being pretty low, it's not like these electric cars are completely unrelated to the normal ones. That's why you see strange packaging issues that you don't get with a Tesla, such as the lack of a frunk.
BMW is also taking this approach, with the X3-based iX3 and upcoming 4 Series Grand Coupe-derived i4. This is partly because studies carried out in Europe showed EV buyers are looking for conventional styling.
The W206 C-Class prototype may also be a brand new plug-in hybrid model, with the current generation already being a rare member of the diesel-electric family. This theory is supported by the presence of a grille opening on the car. The efficiency of the 2021 range will be helped overall by a slightly lower overall weight, helped by increased use of aluminum constriction.
Also, we have a sneaking suspicion that all the W206 models in Europe will use mild-hybrid 2-liter engines, hopefully excluding the AMGs. Despite still having the smart brand, Daimler needs to eke out every gram of CO2.