Well, the spinning of the hard drive is normal it doesn’t matter you connect the drive to the computer or to any of the host device if the power source is connected it will lead to spin the platter of the drive as to make the drive stable so no need to worry about it and if you hear any clicking noise,scattering sound or heavy vibration then you should try contacting WD’s Technical Support about this.
I am having a similar experience with my Seagate slim drive. It’s worked fine for years, then it just started skipping and will not read the drive. I’ll more than likely take it in to the hardware pros, but it’d be nice to make sure my drive is okay. The light at the bottom the drive case blinks quickly like it’s powering on and off. It usually stays lit when plugged in.