Got Service Engine Soon (SES) warning today

[bulkwarrior]

My 06 X5 4.4i got a SES warning this morning right after I cold started it. The car seems vibrates quite a bit. I shut down the engine and restart it, the light's gone and there's no vibration anymore. Does anyone know what's the problem. I could take it to BMW dealer but I'm really busy during daytime and have no time for this.
This is the 2nd time this happened. Last time(last week) when I started in the morning, it also gave me a SES and vibrates, but runs ok if I restart the car. It seems to have something to do with the temperature. When it's near freezing temperature, it's more prone to this problem. Warm start never gaves me any problem at all.
I'm thinking maybe the tech who did the oil change last time put too much oil in. It's a little bit over the "max" mark. Maybe some oil fouls some sparkler plugs and some cylinder misses, which causes the problem. When I have time tomorrow I'll pull up the sparkler plugs and see what's their stats.
Any inputs greatly appreciated!