Car stalls when slowing down/stopping, codes U1000, P0868 and U0100?

Vehicle starts up great but every single morning when the engine has sat overnight, I will start it put it in gear(reverse/drive) and it will studder and stall does this a couple times than allows me to drive off I get the first 2 or 3 stops signs and will stall at each one of them. I can bypass the stalling by putting it into neutral or not coming to a complete stop. After those first couple stalls it won't do it the rest of the day. I have also noticed when I'm driving and have my foot steady on the gas at consistent speed, I can feel the vehicle accelerate and decelerate slightly on its own. Had the throttle body and mass air flow cleaned but it didn't seem to make a difference. 1 mechanic told me there were 3 stored codes on the transmission u1000, p0868 and u0100. After driving to work one day on the interstate my car stopped accelerating.I had it towed and a different mechanic said they didn't see anything wrong with it, that it didn't stall and drove great, after the tow it stopped stalling in the mornings for 5 days and started again every day since.