I think what you are feeling is that car will not get lock up. If you count the shifts, I bet you get four. Fourth gear is overdrive. There is a sensor in the transmission called a TFT ( transmission fluid temp ) sensor. The way our transmissions work is that once 4th gear is engaged and there is a semi consistant speed that is not too demanding, the torque converter applys a clutch inside. That is called lock up. Lock up gives a nicer ride, better fuel economy, and is when the transmission cools itself most. Without lock up the clutch and fins are slipping inside the torque converter, generating heat. Lock up, lets things cool down.
So, it only makes sense that if you want the transmission to heat up quicker, the easy way to do that quickly is prevent lock up.
I think that is what you are feeling. If in fact it is not getting fourth gear, you have a problem.
Mike