External Hard drive "hunts"

I converted from Hard Disk Drive to Solid State Drive. The Hard Disk Drive was installed in an self-powdered enclosure to serve as an offline backup. After backing up my data, the drive "Hunts" (I hear the read/write arms cycling.) Any way to stop the cycling?
Its not a real problem. When I want backup, I power up the enclosure, perform a backup, and power down the enclosure. With no power the enclosure, data can't be stolen.