What do I do when an MacBook Pro is overheating?

Short answer, if your Mac is not shutting down on its own then it is not overheating.

Longer answer:

Read About fans and fan noise in your Apple product - Apple Support. Incorporated in the links with it, you will eventually find this passage from Keep your Mac laptop within acceptable operating temperatures - Apple Support:

"If your Mac laptop gets warm even when it isn’t doing tasks that require intensive calculations, or if it has fans that run for a long time, use Activity Monitor to check CPU activity. Look for malfunctioning processes that can put a significant load on the CPU and check for unexpected fan use. If issues persist, close and open the lid on your laptop, or restart your computer. ..."

Post a screenshot of Activity Monitor if you wish. Use the Energy pane, or CPU sorted by %CPU in descending order to see which apps or processes are using the most energy or placing the greatest demands on your Mac's CPU, respectively. To show the most relevant information I suggest selecting "Active Processes" from Activity Monitor's View menu.

Other thoughts addressed in the above Apple Support documents but are not emphasized enough IMO: never use cases, covers, or "skins" on a Mac.

Hi blessedali,

Thanks for posting in Apple Support Communities.

With your Mac becoming hot when in use, make sure that it's placed on a flat table or desk to allow circulation to flow. Open Disk Utility and check whether you have any tasks in the CPU tab that has been running a long time or running high. Depending on the task, you can quit it and allow your Mac to run to see whether this behavior continues. Restart your computer to refresh running processes.

View CPU activity in Activity Monitor on Mac - Apple Support

Regards.