Sentence rewritten to be convoluted:
"Self-absorbtion could be the real explanation, as I may have mentioned before, regarding certain people's perception of their personal quality in the area of empathy, specifically their supposed superiority in that regard."
Original sentence:
"I have probably mentioned this before, but if you think you are unusually empathetic, the chances are that you are actually fairly bad at empathy, but are too self-absorbed to notice."
Remarks:
It is not the length of a sentence (or paragraph, chapter, etc...) which makes it convoluted. Rather, it's in the flow of the ideas. A sentence will be more difficult to understand if the reader must hold several supporting ideas, or even a conclusion, before the author has delivered the subject being commented on. A logical, linear progression of remarks is easier to follow.
Or, to propose a metaphor, if you start building a building from the roof to the floor, you have to hold everything in suspension until the foundation is put in.
Some ideas, admittedly, are not linear concepts, and finding a logical order of presentation can be challenging, or even impossible. But in most cases, it is possible.