Why does power go off immediately after turning it on?

"my laptop turned on for a second or two but then turned off. when i started it up it showed the hp logo an before i could do anything the laptop turned itself off. sometimes i would turn the laptop on and it would go into windows repair mode, i noticed at this point the laptop would stay on for about 30 seconds or longer before turning off.

The charger was the issue with my laptop. when i first got my new charger and tried to turn the laptop on it would just restart within 1 to 2 seconds of turning it on. i did all the hard reset resets but it was still the same it would keep truning off. i then left the laptop on charge for about 15 minutes before returning to it and when i pressed the power button the laptop started up and went into windows repair mode, when it did its repair thing it just asked me to restart the laptop or go into advanced option. i restarted the laptop and it started up first time, it hasn’t turned off on me yet so i hope its been fixed.

hope this helps others too."