As with most Mercedes problems I can see this one is of a technical nature.
I think the mouse, clearly of german origin, based on the picture posted above has decided to take up residence in your vehicle for a reason.
I would start by getting into his/her head by profiling the mouse. Why this car, why now, why the trunk, why not eat the brown bread? Is the mouse acting alone? Does he or she seem like a loaner? Any behaivoral changes? What motivates this mouse.
Is there a mutually beneficial resolution that can be reached?
Think like a mouse, he/she is probably desperate at this point, capable of almost anything. Are you in danger?
Maybe this mouse is sick or unballanced, maybe it's got rabies??
Maybe the mouse is not the problem at all, maybe it's you??
I would think about all these things, test stuff with a volmeter, measure some clearances, drink a twelve pack, rotate the tires and you should be all set.
Glad to help,