2005 X5 4.4 in trouble
 

Yesterday my X5 started throwing uo transmission failsafe mode and engine made. Runs very rough. Let it set and while on the phone to AAA it started back up. I drove it home about a mile and it started it again just as I git ti the house. Still doing it. I charged the new battery jusy in case it was losing power. No Go. Any ideas ? I really dont know much about this beast. I am used to 3 series. Where to start looking ?

Read diagnostic codes to start with?

Yeah, it can be so many things, start by checking what codes you got.