This may help.
Control Panel > Power Options > Change plan settings > Change advanced power settings. In the window that opens, scroll down to USB settings > USB selective suspend setting. Here, change the default value of Enabled to Disabled.
I have been using this for about a year. I do have it plugged in a USB 3 port. There are a couple of other things you can do that may fix it.
In Device Manager> Universal Serial Bus controllers> Intel USB 3.0 eXtensible Host controller-1.0 (Microsoft)> properties>Power Management tab> uncheck...
On the desktop Click on Control Panel. Then AdministrativeTools >Component Services >Serveries(Local) >Double click on Computer Browser >In Start up Type >ChooseAutomatic >Check apply then OK. Then restart computer. Do the same thing for UPnP Device Host. Hope this helps.
I don't know what kind of drive you have, but I had the same problem with a WD external USB 3. I called WD and they said to go in Services and change Computer Browser and UPnP Device Host to automatic instead of manual. That fixed mine.