The phone will heat up when using power intensive applications and downloading large files, shooting 8k video for extensive period will stretch it. in this article user had warning not to record in 8k over 5 minutes. May be advisable to turn off any connections not needed when shooting 8k. https://www.digitalcitizen.life/recording-videos-smartphones/ As already mentioned lower resolution should be fine in most instances.
Over heating guide here, as long is device is cooled down generally should not be an issue. https://www.samsung.com/uk/support/mobile-devices/what-to-do-when-your-phone-heats-up/
I do not work for Samsung or make Samsung Products but provide independent advice and valuable contributions.
My Device- S21 Ultra 5G ( SM-998B/DS ) CSC= BTU , 12GB/256GB
One Ui 4.0,Android 12 Official Version.