When I first started Zoloft, I got hypnic jerks, too. They go away. Just give it time. They can't kill you. I would advise maybe using something to help yourself get sleep if the problem persists too much. I used Benadryl when the insomnia was the worst, but there are a lot of choices.
Perhaps asking your doctor about something like Vistaril could help you. It's calming for anxiety and makes you tired.