iMac 27" (2009) constantly reboot

[MaccoMac]

Please Help!!!
My mac is constantly rebooting, sometimes I can log in but cannot go any further as it will reboot again.
This started when I boot up in safe mode and want to log in, it reboots, since then it being rebooting.
Some text appears as it reboot but it's disappears fast.

 

[MacOG728893]

While Apple Hardware test isn't always the most accurate, it can help diagnose the issue if it's hardware.

Run it and see what results you get! http://support.apple.com/kb/PH11342

Believe it or not, it could also be software related. While we are all more accustomed to Windows having errors commonly that need a re-install, it can happen on OS X as well.