How about ...

1. Chips not clearing.
2. Kerf pinching the blade.
3. Dull teeth.
4. Teeth too fine.
5. Teeth digging (sticking) into the leading edge of the cut.
6. Orbital setting incorrect.
7. Sawing into something hard (like steel) on the bottom side of the cut, such as the edge of your table saw.
8. My personal favorite ... trying to make a cut while not realizing the power cord is preventing the saw from moving forward, such as the cord getting caught up on something or wrapped around something. For me, it's the one and only reason I mysteriously can't get a cut to progress with a jigsaw, circular saw or router.

Ken Blanton