Girls, please tell me what to do. My daughter is 3 weeks old and for a…

Girls, please tell me what to do. My daughter is 3 weeks old and for all 3 weeks, excluding days in the hospital, she cries very hard when she sleeps and arches her back. This happens every time she sleeps, she cries and then falls asleep again. She doesn't wake up because of this. It can happen every 20 minutes of sleep at most, the maximum she can sleep without crying is an hour. What could it be?