Thanks for the replies.

The vehicle has approx 165,000 miles on it. A tranny flush was performed about a year and a half ago at around 145,000 miles by a well respected local BMW indy. This specific issue only surfaced of the first time yesterday though. No visible oil leaks from the transmission.

I should note that on rare occasion these last couple months when I put it in drive and let off the brake, I've been getting the "secure vehicle from rolling" msg as it kicked it back into park. I haven't had it pop up super recently though...

I own a Foxwell NT510 but the damn thing crapped out a little while back. I did throw my generic OBD2 reader but to no surprise it didn't give me anything useful. I'm ordering a new NT510 or 520 today and will see what it tells me, before bringing it into a shop.