The HMC 150 book, by Barry Green, says: "...This is completely normal, there's nothing wrong with the camera. What you're hearing is an element of the optical image stabilizing (OIS) system. When the camera is powered on, the OIS system is energized, and the rattle disappears."
Funny. I was just thinking yesterday about making a post for old times sake about the click /rattle sound to bring the once familiar question into 2020 but then saw this post