Phone restart almost every time, if we use bluetooth while disconnecting whatsapp voice calls
It sometimes happens with normal voice calls too while disconnecting call using bluetooth
I believe this is connected to this issue even though you're the first one to mention WhatsApp. Try and see if setting the BT volume to 3 out of 7 fixes the issue temporarily. A fix will come with the Android Q FOTA
Did the BT volume to 3 out of 7 temporarily fix your issue?