at times the service engine light will come on, and then go away, then at times when l fell up the gas tank just a little over the full point the engine light will appear again,what could l do? and make it go away?

Replace the gas cap.

l would not fool around with a service light that is coming on in a BMW.

See your mechanic.

Try this-Undo the gas cap and then put it back on. Make sure it is tight.

if the gas cap is fouled somehow, the fuel system could be experiencing vapor lock, which will set off bmw is overly sensitive engine trouble code. another thing..this happened to mine, it could just be an o2 sensor. like l said. sometimes bmw is trouble light seems like it is on crack.

l would suggest as everyone did that its the gas cap but l had the same thing and it turned out to be a vacuum hose leak and l dont even know what it is l had the car in bmw to get a crank sensor replaced and they fixed that too for no charge