long putter kit

long putter kit
1997 pontiac bonneville. What causes a transmission to work then not to work?

I have a 97 pontiac bonneville and I went out today and my transmission was puttering on the highway and it just gave out. I hit the gas and it didnt move. Then I let it sit for a little while and started it up and it went back into gear and I was able to drive it. I drove it for about 10 seconds then it gave out again, i hit the gas and it didnt move. I let it sit again and I was able to drive it again. It worked long enough to get me home. Does anyone know what it could be? I put a new kit and transmission fluid in about 3 months ago so it cant be bad fluid. I just dont understand, usually if a transmission goes, it goes completely. Why would it work then not work then work again. Could it be the transmission pump? Thanks
I have checked the transmission fluid level and its fine. It was a little low but nothing major.
I put in a new kit and fluid 3 months ago and the car ran fine all this time up till today. All of a sudden I couldnt drive it.

how did it work right after you put new oil in I suspect the oil is burned