Question Dell Persision [Precision?] M6800 - Won't stay powered down.

Hello, I have a Dell M6800 that I just got returned to me from an eBay sale that has a weird issue. The laptop did not have this issue when I shipped it.

With a battery installed or with the power adaptor hooked up the Laptop will not power down by button or windows shutdown. It will turn off like its supposed to and then 30 seconds later it will boot back up.

I am pretty seasoned in working on computers and this one has stumped me.

Any thoughts?