2004 X5 wouldnt start today.

[DINANM3]

I went to start my X5 today and the alarm went off and it wouldnt start. So then I thought maybe the alarm was on somehow. But then I got out shut the alarm off. Locked and unlocked the X5 again went to start it and the same thing happened. Then I looked over at my nave screen and it was asking for a 4 digit code. So then I start looking in my glove box for a code. None anywear. Then I call roadside and they said they had no idea what it was so they sent a tow truck. In the mean time i called the dealer talked to the service manager and he said he had no idea what it was. So I hang up with him. So I tell myself there is no way im getting towed for some stupid shit like this. So I put in 0000 for the code and pushed enter. I tried to start it and it fired right up. It hasnt done it sine and i must have started it at least 10 times since since then. Does anyone have anyclue what the hell happened and If i should be worried about it happening again. Also what is that code for and where do you get this code.