My battery just died after 5 years in my X5. Happened to be in -15 F weather being outside while at work. So I went to Auto Zone and bought an ATG gold battery almost with OEM specs. All the things you are experiencing happened to me and eventually my car wouldn't even turn on. Completely dead. So I replaced it this morning and it started right up instantly like a brand new car. No lag or delay or anything. However I need to register it this week and I should be good to go. Looked all over Bimmerfest forums and they have a bunch of X5 E70 problems such as this. I knew my battery was going. lol Plus in extreme cold weather older batteries die faster. 36 is pretty warm. I wish it was that hot here.
