I have a 5yr old Mac Book Pro. I didn't have it plugged and had shut it down. When I went to open it I found the whole laptop was heated and couldn't get it to turn on. I left it a while then plugged it in and finally it turned on but registered the battery was at 0 charge. Do I need a new battery or is it an internal problem. I left it for about 5 hours and restarted and recharged and seems to be okay again. I'm worried about damage to overheating. Any assistance would be greatly appreciated….Thanks
As Rob said, your lid switch might be the problem.
I would suggest following steps:
Reset your SMC and the PRAM/NVRAM.
Run Apple Hardware test to see if it comes up with anything.
Check your Pmset -g profile.
There are 2 small magnets mounted on the lid (along the top edge)
You can find them by using paper clip.
On the opposite side (of closed lid) there are 2 sensors, that normally should last forever (unless you put a strong magnet on them so they are stuck now), but then there is nothing that does.