2016 st3.
There are two buttons to the right of the light switch next to the steering wheel. This is for daytime mode and adjusts the brightness from so bright that it almost hurts your eyes during the day, to so dim that you can hardly see the screen (this also effects all the other dash lights etc.).
In the infotainment settings. You can choose whether to use auto dimming at night, or not. You can also choose the level of illumination for night time mode and this again (at least on my car), has a very wide range of settings.
There is also a button in the middle of the dash (bottom right hand corner of the climate control labeled DISP) that blanks the infotainment screen completely, should you wish.
What doesn't work quite as well as it maybe should. Is that the auto dimming doesn't just appear to switch straight from daytime mode, to night time mode as it gets dark. It looks to do it in a couple of stages. So if for say it's a bit overcast, it will dim slightly. If you then go under some trees and it gets a bit darker, it will dim further. I at times can find this a bit distracting. It's also maybe what you are mistaking for the screen at times appearing to "refresh". This is certainly how mine works and the other two face lift ST's that I've driven. Cant speak for the pre face lift model.