Galaxy A51 suddenly reboots contantly unless in Airplane mode.

Thanks for any insights. I have already purchased a cheaper Cricket phone until I fix or give up on this one…

A few days ago my Galaxy A51 5G (which had been fine minutes earlier for calls/texts) suddenly restarted multiple times in a row. After maybe 5 minutes of this, it stayed on but told me there was no sim card installed.

I manually rebooted and the same thing happened - multiple consecutive reboots, until finally it stayed on but told me no sim card was installed.

I subsequently figured out that if I put the phone in Airplane mode, it would stay on and let me work via Wi-Fi for maybe a few hours before rebooting itself again and again.

I removed/reinserted the SIM card, reset the network settings, uninstalled all non-essential apps, booted to safe mode (still would not recognize the sim card), and went to Cricket and purchased a new sim card. None of it helped. 

Then I did a factory data reset, but still the same issue.  

I found threads for A51 restarting on Samsung, but they were not specific to the SIM card/network being on and didn’t address the issue.

Any insights before I consider the phone a loss?  Anyone else have this issue?

Thanks,

JCHP