My advice is to get it ASAP to service. Like... as soon as possible! And not use it at all until that point.
Not because of something "important", but because you might get injurend.
And the second reason because sooner or later it will turn your laptop in to a toaster.
It could be a loose wire, a bad connection, a bad wired connection or many other little things; Or something with the power moddule or battery. Impossible to tell. Most lilely somethin fixable in 5 mins after debugging, but I don't think you're an electrical engineer or else you wouldn't have posted here.
So... Get your laptop in to service. If you bought it new you might be able to benefit from Asus' DOA policy (here it's 7 days since purchase).
