My iPhone 13 has suddenly started reporting "No SIM" randomly on a daily basis. If I restart the phone, it usually starts working again. There has been no damage to the phone and I have never taken the SIM card out.
If the SIM card is old, try getting a new one. Hopefully this doesn't mean your phone is dying. There's troubleshooting on the Verizon website if it's a Verizon model phone which you can access through your account, otherwise may be something you'd have to look up with Apple Support.
