When you refer to "CSS", are you talking about Churg-Strauss syndrome (CSS) as a possible cause of these internal vibrations? MAYO CLINIC describes that condition here: https://www.mayoclinic.org/diseases-conditions/churg-strauss-syndrome/symptoms-causes/syc-20353760 Perhaps you were referring to a different "CSS" condition instead? By the way, there are two internal vibrations/internal tremors groups on facebook, but one of them is for the during-sleep-only type of vibrations and the other is for internal tremors, more generally (24/7 vibrations). It is amazing how so many people got these vibrations from post-covid long-hauling. Mine started with a different cause, but there really has been an uptick this past year, it would appear. My vibrations only happen during sleep. Thank you in advance for your answers, experiences and input!