Q: 2002 chevy Tahoe Transmission Mystery

O.K., I was driving around 40 to 45 mph , the transmission shifting smoothly and all the sudden I thought I was rear ended. I let go of the pedal, looked around and gave the vehicle some gas but the transmission was in neutral so it felt. No whining, screeching or clunking, just RPM's. I was in drive. D on the column. I pulled over to the side of the road. Put in park, it engaged just fine, still no noise. I moved the lever to Reverse and it engaged, no noise, grind or anything. I put it back to D and it engaged no noise anything. I drove on my way and thought maybe it popped out of gear. Fast Forward 3 days later it did it again. Exact same scenario only this time it would not work in D after stopping and trying to re-engage the column. I placed it in 1st manual and it took off just fine no noises then progressed to 2nd then 3rd. It shifted all 3 gears no issues. It just wont work in Drive all else works fine. Never any noises. What do you think Servo, Switch. Where to start?

My car has 240000 miles.
My car has an automatic transmission.