@awesomeanji: I'm sorry to hear that you're experiencing this issue. Please can you restart the Note 10+ in Safe Mode, and monitor the performance for a little while, depending on the frequency of the restarts. This will disable all third party apps, and help to determine if the problem is stemming from an external source.
To enter Safe Mode, press and hold the Power button until the 'Power off' prompt appears on the screen then release > Touch and hold Power off until the 'Safe mode' prompt appears then release > To confirm, tap Safe mode > With Safe Mode enabled, ensure Airplane Mode is turned off.
If you notice that the phone no longer restarts while you're on a call, restart the phone as you would normally and uninstall any recently installed, third party apps. Sadly it isn't possible to determine which app is causing the issue, although you could try checking Settings > Battery and Device Care > Tap the graph symbol in the top right > App Issue History to see if there are any repeated issues with a certain app. I hope this helps.