Hi,
If you are on the latest firmware version which is:
Version WW-17.0240.2009.47
Try factory reset once.
Temperature can fluctuate depending upon the ambient temperature. During Ideal normal process the phone shouldn't heat.
If it doesn't help I would request you to visit the nearest service center:
Due to the lockdown, service centers may not be functional. Kindly call the service center before you visit one.
https://www.asus.com/in/support/service-center/india