I use small, cheap die grinders from Harbor Freight for inertia sanding. They are small and cost about $10 when on sale. They may not be great die grinders, but the bearings are good and they have a 1/4″ collet that accepts my 2″ hook-and-loop pads.
Inertia sanding is when you hold a sanding disk to the wood while it’s spinning on the lathe. The turning wood spins the sanding disk so you don’t get straight scratches. It’s less aggressive than power-sanding, and can produce a better finish than plain flat sandpaper.