Is your Legion a laptop? (Is the WB Back drive not a 7200 RPM 3.5" drive?) What specific model of Legion do you have? Confirm you have managed to squeeze a 3.5" drive into a laptop?)
Assuming you even have internal space for a 3.5" desktop drive, your laptop might not be capable of supplying enough power to the larger desktop drive, as 7200 RPM drives often can consume/require 30 watts or more when merely spinning up...
Or, it could be failing, as often failing drives will basically almost hard lock a system up (or slow it to a miserable crawl)when trying to read/index/inventory the files contained on it....