my lenovo ideapad 520 turn on and off rapidly

Dec 27, 2018
hello guys i was searching on facebook in my lenovo idea pad 520 ( bought it about 8 months ago, and suddenly it turned off, and on, and off
it turns on for 3 seconds and then there is a sound of a knock and turns off again.. it continue like this untill now and i dont kno what to do im really afraid its lost, i have important things over there:(
i tried to press the power botton for a while but it keeps doing that

i was recording a video of that from my phone but i don't have an option to upload it here ..
what do i need to do?
thank you:(