Hi there geraqui,
Do you need the data on that drive? Are you sure the drive is in a healthy state? Do you get some sort of an error message?
One thing you can try is to go to BIOS and adjust your boot priority. You can leave the SSD to be the only boot option. In case the issue persists and your system won't boot with the HDD attached, then there could be something wrong with the HDD.
Attaching the drive with different cables to another port will not hurt.
If you don't need the data stored on the drive, you can try to wipe it with some third party HDD wiping tool.(from a flash drive let's say)
Let me know how this goes,
D_Know_WD