I was having a lot of trouble with TB freezing nearly every time I used it, although it was letting me kill it with the Task manager. What finally worked for me was to go into the account (right click on email account name) then advanced, then folder subscriptions, and uncheck the All Mail box. Apparently that is the archive box for Gmail accounts (which I have) and it had saved everything ever sent or received and was constantly downloading into that folder. once I did that it hasn't happened once. May not be your particular problem but couldn't hurt to try it.

Thank you drmeow for you help but this does not remedy the issue I am having. Thank you again for your suggestion.

What is your anti-virus software?

christ1, I am using Bitdefender Total Security 2020.

Try to start Windows in safe mode with networking enabled.

Still in Windows safe mode, start Thunderbird in safe mode. Does the problem go away?

Note, Windows safe mode isn't a solution, but a troubleshooting step.

This issue is intermittent and I am now considering it resolved. Thanks to everyone who provided input to the issue. Have a great day and stay safe.