I get that too, Peggy. So frustrating! Sometimes I can sew for quite awhile without it, and sometimes it's every few stitches. There was a thread a couple weeks ago with suggestions on how to stop it from happening, but I haven't tried any of them yet. I'm not going to bother taking mine to my dealer because I have zero confidence in their competence, and I know they will just try to sell me a new machine...they are totally about machine sales. 
Lisa