Misfire after misfire

Hi. My english is not too good but I hope you gonna understand me.

I just bought grand caravan from dodge dealership. After 2 days check engine light show up. Cylinder 1 misfire. Mechanic replaced coil and spark plug. But then comes another one misfire number 3. I don’t know what to do, estimate cost to replace one os 120$ but I’m worried after that gonna come another one and another. Mechanic said it may cause after engine wash by dealership. I’ve got implied warranty and I’m not sure it gonna cover this issue. Dealership is 70 miles from my home…

what year is this Dodge Caravan?

What exact engine do you have?

This is 2014
V6 3.6

Anyone know something about that? Any solutions?