So I don't mean to be a harbinger of doom but:
I went through this with me 2016, I had about 15k miles when it started to happen and I would just change the plugs out to make it go away. But it would come back. After the 3rd set of plugs in 10k miles I started to get suspicious, so I was pulling the plugs out and my #2 was stuck in the head. Long story short, Ford replaced the engine. There is a well known issue with coolant intrusion into our engines but you mainly see it in the escapes and fusions, Ford will just replace your engine if you are under warranty. You can find out if you have coolant intrusion by removing your
spark plugs and inspecting the cylinder for coolant / wetness. My #2 was very wet when I finally got the plug out and the plug had rusted to the head.