Recently, my hard disk drive (bought with the laptop) simply vanishes from the list of devices in Dolphin File Manager. It is happening more and more often now and obviously, I am not able to access or save my files on the HDD. Usually it comes on again when I reboot the machine. Is there any fix for this type of behaviour?
It could be various reasons, first see if your disk is available under the command 'df -h'. If yes, it could be bad sectors and you may have to run fsck from the terminal (let me know if you could see the disk in the above command).
If not, take help from a technician who will shut down the laptop and examine the hard disk (mostly loose connection as you mentioned it sometimes work!).
If that doesn't help either, then you may have to replace the HDD or consult RDP.