Well the title says it all. After the GUI button of shutdown responded to reboot. I have tried all the command there is but every time I shut down my laptop it reboots.
I tried
sudo halt
sudo poweroff
sudo shutdown -h now
I have a dell vostro 3400 with i3 and 4 GB RAM if that matters. Has anyone faced this problem. It was doing fine with 10.10
EDIT: Ok, seems like I can confine the problem to prevail during laptop usage from AC only rather than battery. As suggested I tried updating bios with the help of this but couldnot succeed.