Noticed my baby arms were shaking/twitching

Jennifer • Married 10/4/14 SAHM with 2 girls❤️
My MIL was holding my daughter yesterday and she was asleep and we noticed both her arms started to shake. They were shaking like she was having a seizure but it was only her arms. So I wake her up and she stops but it scared the crap out of me! I tried to google it and think it is normal for babies to do that when a few weeks old. Has anyone else experienced this before?