Internal secondary drive keeps disconnecting "randomly" and it is not detected anymore

I have a Seagate secondary HDD and a principal SDD.

Sometimes the HDD disappears without even an extraction notice, it can happen anytime in idle or when working. It does not appear as a pop-up extracted or disconnected it just disappears

I think this problem started when I upgraded the SO to windows 10. Before I had for a while the same pc with windows 7 and i did not have any problem at all, since the upgrade (which I need to run some work programs) I think it started doing this.

Once the HDD disconnects is impossible to get it up and running again until I restart the pc, and here is the troublesome part for me. Sometimes (not everytime the drive disconnects) I can get into the bios and check that the drives is there, and when windows starts, the HDD starts to keep restarting itself (turning on and off continuously), windows take a while longer to load and can't detect the drive from the start, when this happens, I can only make it detect again by unplugging the drive manually and connecting it again once windows has started. On the other hand, sometimes it solves only with turning it off and on.

I've checked with crystal reports and SEATOOLS for any trouble in the disk. With crystal reports it says that the health of both drives are good, with seatools i can take on any test (if for some reason it does not get disconnected during the test) and pass it without any trouble.

I've also tried to change the SATA cable, the SATA position, changed the power connection. Any idea what can be the cause of this problem?

Things like this are very often the cable/connections.
Test cabling again - use contact cleaner on plugs & sockets [with power off, of course] then ensure there is no stress at all on the sockets at either end. Even if you have to rest the drive on something for now to keep the cables straight.
Those mobo sockets are horribly fragile & can cause a myriad issues if the plugs don't sit dead square into them.

UPDATE: check below for the definite problem i had

It seems kinda solved, still some problems. But here is what i did:

1. Secure all the connectors in the pc, motherboard, hdd, etc. Seems sometimes useless, but checking everything you migh found a weak connected or something like this. Also check for anything wrong with the motherboard like burned components or so.
2. Check the hdd if it works in another pc, or if you can connect it external. I used an old laptop disk that i can connect by usb and plugged it like a secondary, it did exactly the same so as the main one, so I plugged it again as usb and it has no trobuble, so i guessed it could not be the disk.
3. Update windows, here was the main probblem there was an optional intel update which the system could not install and failed at like 13%), so...
4. Windows restorantion and update all
5. Once everything is updated,the hss could work well. If is not working, format from scratch the whole hdd and reformat it in slow mode, it may have corrupted files if it has turn off and on while writing.
6. Once the format is done, do some test (seatools or the brand program), see if there is any trouble still
7. Check that the hdd can work, i got a huge file and started downloading in the clean HDD

So far is working ok, and i was going to throw away the hdd for what it seems some software problem. Hope this helps someone!

UPDATE:

after a long time i discovered it wasn't only windows fault. My powersource was faulty, it seems that sometimes didn't provide enought energy to the HDD turning it off. Later when giving power back the HDD worked again, but then windows do his thing and did not allow me to reconnect the device, thus having to do the above. That's why i thought it was windows fault. In linux setup worked fine, seems my linux setup allows reconnection of secondary drive.