It might be a sign that your hdd is dying. run a smart test on it with
CrystalDiskInfo
Usually such hdd's die within a month. So i suggest get a new higher capacity hdd and copy all the stuff you think is important. If you have some usb drives lying around with free space on them, copy on those too.
Edit: On second thoughts, if you're hdd smart status shows up fine in the above software, then most probably, the hdd must be idling its heads if there is no read/write access. Might be due to some power saving options in your windows or inbuilt in hdd. In windows power options, change the idle time before hdd sleeps to 20 or 25 minutes. It might help.