I am confused. Why would you constantly be going back and forth between overclocked and stock? If your overclock is stable there's no reason to ever do this, especially at stock volts with your temps. Have you tried to see what happens if you just leave the overclock alone? it should still switch to the 2d clocks when not in use. Sounds like a driver issue
You don't HAVE to use it all the time, but games are the only thing that would unless you do some gpu processing for other stuff.
What should happen when overclocked is when you apply a load to the GPU it should clock up, when you stop the program it should return to 2D clocks, just like it does at stock. Since you haven't changed the voltage at all and temps are low there's no reason to not leave the overclock on, or to turn it on and off just for games. It wont affect the life of the card at all, and it should only run that speed when its being used.
So if the problem is related to you switching back and forth you can try leaving the overclock set and see if it drops correctly. If so it can be set at boot automatically. And would save you some unneeded hassle constantly switching. Unless you have a special use case you shouldn't need to do that.
You should update the drivers of course as well, that's more likely the problem as the clock settings shouldn't affect it switching anyway. Unless you forced them.
I did what you say and you're right, the gpu returns to 2D Clocks (300/300).
When i use firefox (youtube,etc) my clock goes up to 300/1000 or 600/1000 by stepping i guess.
But i have another problem here, i use 1.175vm and for some reason, it never go back to 0.95v, even when iddle, that's why i kept turning overclocking on and off in the first place, because the tempeture stays at 54°C or more, anything I could do?