CPU temperature is 72°C, how can I find why?

It's been a while since I noticed that but I can't find the reason. I selfhost :

• a linkding with docker
• a writefreely
• a bludit blog
• a CalDav (radicale)

There is a syncthing running for backups done with borg at night (automated with a crontab).

When I htop, I don't see anything to hint me to what is causing the heating.

Any ideas of what I could do to investigate that?

Thanks a lot.