I dont't really think it is nightmares that your newborn is going through. Imagine the baby has been in your womb for at least 38-40 weeks that is a long time. And now she is out of your womb, she has to adapt to many external changes and she is just 7 weeks old.
Did you wrap her up before putting her to sleep? Do you let her sleep in her cot or in the hammock? Do you put a beanbag on her chest? Do you sleep in an aircon room? Make sure that the temperature is around 24-25 deg C. All these help to comfort her......as like providing her a sense of security.