You may be facing some connectivity issues. Is this a new hard drive or you have been using it some time? If the laptop is under warranty, contact the seller and ask for guidance.
If the warranty has expired, I would open the laptop and check if the hard drive is properly placed. Remove it and reconnect it back. I strongly recommend you to backup all data the next time you are able to boot. It is really hard to tell you if it is a HDD problem or a laptop problem and, as xpcman said, you may need to consult a technician.
Hope this helps