It will always be warmer than you’re used to, because internal heat is purposely routed to the exterior frame in order to keep the internals cooler. If it gets a LOT warmer than its normal warmth, then contact support@puri.sm to find out what might be wrong.
See: Librem 5 Battery Life has been Doubled - #10 by Sarcasmo220
They’re sending out this fix within a few days, I think.
As @OpojOJirYAlG said, make sure you have applied all waiting updates, by either tapping them to download and install from the PureOS software (store) app, or in the Terminal app, using sudo apt update, followed by sudo apt upgrade if any upgrades are available. Do this often, as many improvements are constantly arriving.
There’s a lot of good information and tips here in the forums, so just search if you have any specific questions.