Eml!!!!!!!!

Hi, i recently bought a BMW 750il. the car has 123,000 miles on it and runs great but alomst any time i'm over 85 the EML light comes on after i've let off the gas. Why does it do this? The cars acceleration is gone afterwards for the most part but is fine after i turn the car off and back on. What can i do if anything to fix this problem? Thanks any help would be greatly appreciated.

Stephen