Handsets usually get a bit hot when they are being charged and this is normal, but when they get too hot to the point where it might be too hot to the touch or when it can lead to the device shutting off by itself, then you know that this is a problem. Unfortunately this is a problem that some Pixel 3 users are reporting.
According to various posts across different platforms on the internet, Pixel 3 users are reporting that their handsets are apparently overheating while they are being charged. It is unclear as to how widespread the issue is, but it is clear that these aren’t necessarily isolated incidents. The overheating can get to the extent where the device shuts itself off which obviously is less than ideal.
Some users claim that this is triggered when the handset is being charged and an action is being done at the same time, like watching a video or making video calls (it seems to be video-related). It also doesn’t seem to be specific to any chargers as it affects both third-party wireless and wired chargers, along with the Google Pixel Stand.
Your mileage may vary on this issue as it will depend on your device. Some users aren’t seeing any issues, while others claim that sending it back for a replacement seems to have solved the issue. Google has yet to comment on the problem so it is unclear as to whether or not this might be a bug that can be fixed or if it could be a hardware problem.