In order to fix USB drive keeps disconnecting & reconnecting, simply follow the below-given instructions:
• At first, you need to click on ‘Windows + Q’ then, type cmd
• Next, right-click the ‘Cmd Prompt’ and then choose ‘Run as Administrator’.
• In the new command Windows, you need to type chkdsk X: /r /f where X is the new drive letter of the drive /r, /f are the chkdsk parameters.
• After this, press the ‘Enter’ to just activate the error-checking process & fix via chkdsk.
• Finally, take out the USB drive and again try to connect it. Then check if you’re able to access your drive.
For More info:
http://www.rescuedigitalmedia.com/fix-usb-keeps-disconnecting-and-reconnecting