2000 Honda Accord 2000 Accord Transmission Problem

Transmission problem
2000 Honda Accord 4 cyl Front Wheel Drive Automatic 115K miles

My Accord (2000 Accord 4 Cyl SE, 114K) is having some weird issues with transmission. I am the only owner and always maintained per mfg recommendations. Couple of weeks back my wife noticed D4 indicator flashing on the dash board and MIL came up. I diagnosed myself, got a 'P0708 Shift Malfunction'. Since I can't fix it myself I took to the dealership. They came up with the same code but said it may be a computer malfunction and erased the MIL code. I thought my wife's driving habits has to do something and thanked god for dodging a transmission replacement. Stupid me, it came back in 2 weeks. This time I was the driver. I started off with a cold engine, rolled out of my driveway and it happened. D4 started flashing, MIL came up. The car wouldn't speed up as I press the gas. Feels like keeping it on Neutral and pressing the gas. The RPM goes up and then suddenly it gets it gear with a thud. It smoothes out as I go over 30 mph and over.

I took it back to the dealership on last Saturday. This time they said I am looking at a transmission replacement. They couldn’t give me the quote right away (but I am expecting it soon). Surprisingly, when I drove back from dealership, I did not feel the same (even on 1st/2nd gear). It drove pretty smooth. Yesterday, I drove around 20 miles and every time I start from a stop or red light the car refuses to pick up and I feel the same. After driving for a while, I went to gym and spent around an hour there. Funnily, when I started back everything was fine as if there is no problem with transmission or pickup. Could it be something related to the heating/temperature, expanding of some metal? Or this is a symptom of solenoid going bad?

I have read a lot stories about this issue. But yet to find the reason and cure to it. Can this be fixed without replacing the entire transmission? If not, would new transmission be guaranteed on this one? By reading, it seems to be an issue of entire 98-02 generation of Accords.