In Chapter 16 - 18 in My Side of the Mountain, what are some things that Sam thinks are trouble?
The chapters in this book aren't actually numbered, so I hope I have selected the correct ones you are refering to. The biggest immediate trouble that Sam experiences is of course the approaching blizzard. Sam has to work very hard to create a wood supply that will keep him warm throughout the entire winter. However, when he has done this, Sam actually finds that he loves winter and greatly enjoys the close communion that he has with animals.
It is when Bando arrives that an even bigger problem rears its ugly head. Bando shows Sam some newspaper articles about him, calling him a "Wild Boy" and stoking the myth of his existence. This of course represents an intrusion of the world of men into the world of nature that Sam has inhabited, and of course, after winter ends, Sam knows that people will be searching for him and will try to invade his tranquil and peaceful existence. This is the big example of "trouble" that is alluded to in these chapters.