Thanks for writing to us.
When did the issue start?
Looks to be a loose connection. Please go to BIOS by tapping on f2 during boot up and check the status of hard drive and let us know.
If possible please re-seat the hard drive . you can get the instructions on support.euro.dell.com--enter the tag#--submit--manuals .
Do provide us your system tag#, email address and name via private message,by clicking on my name in blue and then select send a private message