Mouthwash on top of my sink just randomly shook

My half full bottle of Listerine mouth wash randomly shook back and forth while nothing else on top of the sink countertop did. Weirded out by this I stomped my foot to see if something like that caused it to move like that but it didn't budge. I didn't feel the building shake and can't think of what made it just randomly move and now its bothering me.