When mine started doing it at about 325,000 miles, the dealer re-flashed the transmission and it cleared up the issue. I am still on the original transmission fluid.
2002 X5 3.0 386,700 miles
2014 428i 73,800 miles
2004 325i sold at 123,600 miles
2001 325i sold at 66,000 miles
1970 Firebird Under restoration with no dash cover until Febriary