How many miles are on it?

Have you ever had the transmission serviced? If it's not going in to D or R when cold, or hesitates until it's warmed up I would seriously check the fluid level and if you're over 100K miles and have never had the transmission serviced (pan drop, filter replacement, torque converter flush) now would be the time to do it.

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Current Bimmer
2004 X5 4.4i Sterling Grey Sport/Premium

Past Bimmers
1991 318I Alpine White
1995 740I Alpine White
1991 525I Schwartz
1998 323IS Scwartz
2004 330CI Cabrio Titanium Silver Metallic
1995 540I Schwartz
2000 Z4 3.0 Titanium Silver
2000 330ci Coupe Titanium Silver