sounds like your nvidea graphics card has come loose.
take out the motherboard and 'reflow' the graphics card.
in other words:
take a heat gun that painters use and heat the graphics card up for about three minutes.
the soldering will become fluent again and stick the contact point to each other again.
it's a common problem with the nvidea graphic cards in laptops.
i reflowed a bunch of them already and mostly with good result.
if the card comes loose again just repeat the procedure.
search in you tube for how to do it.
it's a bit scary the first time but it works 9 out of 10 times.
while doing this you will have perfect access to the cooling fan to clean all the dust out.
you will probably find the exit full of dust .
that's why the graphics card gets very hot and soldering connections become loose......
have fun trying.... :-)