I have multiple HDDs and one contains Ubuntu, other OSs and GRUB v2(?).

Anyway, I usually select through the BIOS boot menu which HDD I want to boot to and I noticed a problem when booting to my drive with GRUB on it. The issue is that after I boot through GRUB to any OS on that drive, and I reboot to a different drive (in particular, one with Windows 7), the system reboots by itself after about 10 or 15 seconds.

To prevent this from happening, I have to disable the drives (through the BIOS) I do not want impacted by booting through the GRUB drive before booting to it. I would like to find out why this happens and, possibly, how to fix it.

Thank you.