I would just unplug the 4 mech drives and see what happens with the SSD. Are the other drives in a raid or individual? If they are in a raid there could be an issue with the raid and its repairing when you reboot.
That was the 1st thing I did when this started happening, the SSD drive is like 4+ yrs old( looks like it came out in2011!!!) its a m4-ct256m4SSD1 Samsung. Probably going to replace it with this Samsung 970 EVO 1TB - NVMe PCIe M.2 2280 SSD when I find anew job lol.
went and checked newegg......
might be time to get a new one lol!