Not to point out the obvious...but did you check the oil level? The only time the light has ever come on for me is when I've actually been low on oil. If you're not low, then I'd look at the sensor itself.
Ya my 09 just did it to me last week. It was in the back of my truck for 2 days then fired it up to take it out of the back of my truck and it was on only for a minute or so. I took it out and in the garage, checked the oil level and it was good. I dont know why it was on but it went away....
I just had a thought...Maybe there is a little water in the plug that is freezing and messing up the connection until the engine heat melts it? Could be worth putting some dielectric grease on it to see if that helps.