BMW x5 Suddenly dead question

[Rayx5]

Hey all! Ive been wondering if there is anyone else out there that has the same problem as me.

Two days ago I got into my BMW x5 2002 and it wouldnt start. All the lights on the dashboard came on, (service light, engine light etc). I thought that the problem might be the battery, so I went out and bought a new battery, installed and tried to start it up again, to no avail. It wouldnt start. Just the lights on the dashboard came on. So I left the new battery in and decided that I would have it hauled to the BMW shop. A day and a half passed and I decided to give it one more go, I went in and it started, worked just fine.

This has happened once before, last year; both times when it was cold outside. And I dont use my BMW sparingly, I use it alot when I go out compared to my Acura. I dont know what the matter is and wanted to know if anyone else was having the same problem. If you have any helpful ideas, let me know! Thanks in advance.

-Ray