Air in the coolant circuit

Hello

Subject: Audi S8/D2 2000
km stand 190tkm
Air in the cooling circuit/ slightly increased water temperature.

I noticed this weekend:
At moderate outside temperature (max. 20°) with normal to fast driving a water temperature of around 95°, thus slightly beyond the 90° mark. This Temp. I had then also with vehicle down / running engine. Just don't go to the 90° operating temperature anymore. down.
Both fans run, Termostat also switches correctly. I noticed that more air is pumped into the circuit/the coolant level over the max. Marking had risen. Even when pressing the water hoses, it seemed to me that there wasn't really much in there/except a lot of air...
Turn on heating/ventilation didn't bring much...

Was könnte da sein? Wapu defekt/ Schaufelräder gebrochen? Kopfdichtung? Irgendwas in dieser Art bekannt?

Vehicle otherwise runs perfectly, no oil in the water or vice versa, no water loss, no smoking, fog or anything else...

The next day/day the cooling water level was back to normal...
I have not had a phenomenon so far, since on working days only short-term operation.

Mfg Roland