Internal drive on laptop keeps disappearing

I have a laptop running Windows 10, with a SSD drive as it’s primary/boot drive (C:) as well as an additional 1TB HGST HTS721010 secondary drive (D:). Recently, upon booting up my system, the HGST drive disappears. By that, I mean it simply is not accessable nor showing up in Windows explorer, nor in the Device Manager --> Disk Drives. This isn’t an old system. I bought it brand new in the summer of 2015.

Probably 9 out of 10 system shutdowns/reboots it does not seem to exist. When it does appear, I have tried running local diags on it, no errors found. I have tried to update the driver but it says the drivers are up to date. I am unsure about updating firmware so have not done so.

I have gone into Windows safe-mode (w/ Networking) to try to run diags on it and it shows up every single time in safe mode, but going into normal Win10, it just isn’t there. Because it is also showing up in the system BIOS, it takes a couple of minutes to boot into Windows now. I assume it is trying to access the drive but can’t (thus slowing down the Win boot process). Normally, a reboot or fresh boot up from being powered off took 20-30 seconds at most.

I am at a loss and am not finding very good information in web searches, so I decided to come here looking for help/advice. I’m not sure what other information would be needed by the community or support to get this thing stabilized again.

Any help would be greatly appreciated.
Thanks

To be more specific, it is as if the drive is getting disconnected.

I have seen this sort of thing in a previous laptop that I owned where it only had 1 drive and obviously was not bootable when this happened. However, on that particular laptop, I could see the location on the outer laptop casing where the hard-drive was. When this sort of thing happened, I could simply push in the drive (even though it didn’t feel like I did anything) and the next boot would be successful and it stayed that way for quite a while.

The behavior this time around is very similar, but there isn’t a place on the outer laptop case that is obviously the HGST slot.

Hope that makes sense and perhaps helps with anyone that may have some ideas.