First thing I was taught at a Pfaff convention:
When there are loops on the top, the is a problem in the bottom. When there are loops on the bottom, there is a problem with the top.
This is 'mostly' true. I agree with everyone, raise the presser foot, rethread the machine top and bottom. Make sure the bobbin is spinning in the correct direction and has 'clicked' into the little tension guide.
However, I was also taught to change the needle every 8 hours of sewing and sometimes more often when quilting a quilt with polyester batting.
Let us know how it turns out.