Hi there and welcome
this is a tell tale sign of an impending crash of the hard drive. If your lucky, these are the symptoms you will get else it would just not work one data and you will lose access to it.
To rule out weather this is a software corruption issue, I advise to backup the data off the Drive.
then format the drive (do this by opening finder, then go to Disk Utility in /Applications/Utilities.)
Find your USB drive in the list on the left hand side, and click on it,
Then click on the 'Erase' tab.
Then choose Choosing Mac OS Extended
then use the drive and if it still displays these symptoms, return it to be replaced. I would test it a lot first before relying on it as it may be a software corruption issue, but nearly always its a sign of an impending crash and this will confirm it.