Great tip...."Bird's Nests...
I took a class recently and told my teacher that I always get these "bird's nests" at the beginning of my stitching. She told me to turn the big wheel on the right side of the machine that makes the needle go up and down. She said it helps to make the thread carrier (the metal thingy on the right at the top of the machine, you thread the thread through it, that goes up and down with the needle).
You don't have to turn it but only about 1/2 or so turn and you won't get a "bird's nest" underneath your fabric which can cause jams!! It works every time for me now. The only problem is remembering to turn the wheel! I've been doing it the other way for so long but now I am remembering to do it almost every time I start a seam! Give it a try and see if it works for you!!