My lenovo thinkpad starting problem

After long time i started my lenovo thinkpad, power light on and heard fan sound.
But before window screen appear, automatic off the laptop.
Sometime it start and working normally but mostly time not starting. Sometime off before appear the window screen and sometime off when shows desktop and sometime off in a second.
I already tried hard boot process, after this first time start normally but after that same problem.

Thank you very much. Your advise is helpful for me.