There are 2 common things that cause or can help this issue.

1. The power supply. Time and time again I swap in a monster supply and the machine just works. The owners will invariable say things like "Why?" or "Isn't 400 Watts enough?" but it's a recurring fix for some startup issues.

2. The hard disk has a jumper to limit the SATA speed to 150. I'd try that.

In closing if the BIOS settings are getting lost the recurring fixes (beyond the 2 items above) are to replace the CMOS BATTERY or the motherboard.