Left side ipad pro heating up

Devices do tend to heat unevenly due to many factors including but not limited to: the way it is being held, the ambient temperature of the environment which it is in, (winter day vs hot summer day) and charging recency.

And then also, sometimes devices distribute heat evenly.

(like in this photo)

Why does it matter?

The iPad's internal power supply maybe in this area.

Internal power supplies can get much warmer than the rest of the iPad.

If this condition is NOT affecting the operation of your iPad, then it is nothing for you to be concerned about.

If your iPad doesn't get too hot to handle/touch, the heat is fine.

Electronic devices, like phones, tablets, laptops heat up.