Hi Turn laptop upside down and wrap in towel or bed duvet while switched on for about 30mins then switch off and let cool down still upside down for again approx 30mins, Switch on again and if it works it is a solder problem with your graphics chip on the motherboard it will work for a while like this but you will really need to get the solder reflowed on your motherboard especially the graphics chip.
Let me know what happens.
Yours Sincerely Jeremy
PS Do not sell like this as unfair to person who buys when you know about this fault.
jeremy.belshaw@sky.com Disabled former Forman Electrician latest qualification HNC/D in computing and information technologies.