Notebook starts to boot then shuts down and repeats the cycle

When I try to turn on my notebook the key board lights up, it starts to boot then stops, shuts down and repeats the cycle. The screen does not come up during all of this. The cycle is about tree to four seconds long. It has been suggested that the power supply might be bad. What do you think? Also I am having some trouble getting this thing apart to inspect for loose connections. How do I open