macbook pro m4 external screen closed cover computer heats up severely when sleeping

macbook pro m4 version 15.3.2 Close the cover and use an external screen to connect the typeC to hdmi hub for the screen (because there is an external hard disk using the usb interface). When the computer is not in use, use the trigger angle to set "put the monitor to sleep" and turn off the monitor. After a while, the computer is not running music or playing video software, it is found that the computer is heated severely. This kind of heating is like a large project compiled for more than ten minutes. The cpu usage rate remains at 70% +. Usually, the computer rarely heats up Almost every time this happens, the computer will heat up. I have experimented without opening any programs. The same is true Close the cover and open the external monitor. When using the computer normally, the computer is cold. I usually run idea, two project browsers, more than ten pages, databases and terminal tools are used together, and it is hot when I don't sleep Has any brother met? Is this a bug