Hey so i just got a new car and it has a couple of problems.

1. Took it into the mechanic and he found a bunch of transmission codes, overheating and a bunch of solenoid codes. He suggested it could be the fluid so we got that done. Could the fluid have thrown that many codes? I was having shift flare before that and it seems to have disappeared, but when I’m starting up and breaking it feels as my car is sputtering, which leads into

2. Sputter in park and drive (when stopped, but also sometimes when starting up, or slowing down). Mechanic noticed this when braking and suggested it was probably the spark plugs. Could it really be that? Or could this issue be linked to the transmission?

Ps, I just got an oil change, alignment and replaced the purge valve which threw a code that’s gone now. Thanks!