My old washing machine would shake like crazy but it was just a sock stuck in the drum. I get the leveling advice, but sometimes it feels like people make it into this huge first step every single time. If something's obviously broken or making a weird noise, I'm gonna check the simple stuff first. Not everything is automatically an unlevel floor problem.
Three washing machines in my house shook over the years. Every single time it was a coin or hair tie stuck. Leveling feet are not some magic fix. If the machine is making a new sound, look inside first. Calling it an unlevel floor issue right away just complicates simple repairs.