Slow charging

Hi everyone, I have a Pixel 9 Pro and I've always had problems with charging speed. I tried different cables and chargers (of course also the Google one), but even though it starts charging at a reasonable speed (10 or 20W), it then drops to 1 or 2W (450mA). I noticed that if I restart the phone it starts charging normally, but then the speed drops again.

Does anyone know what could be the problem?