It sounds to me like the thread cutter leaves too short a thread, and that's why this happens. On some machines the length can be adjusted by the dealer, I don't know if this is true for your machine.
I always start by pulling my bottom thread up to the top, and then putting the tails under the presser foot, directing them to the back of my work. I find this stops any thread messes/tangles on the back of my work when starting up.