What is your anti-virus software?

Avast

Try to start Windows in safe mode with networking enabled. - Win10 https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode - Win8 https://support.microsoft.com/en-us/help/17076/windows-8-startup-settings-safe-mode - Win7 https://support.microsoft.com/en-us/help/17419/windows-7-advanced-startup-options-safe-mode#start-computer-safe-mode=windows-7

Still in Windows safe mode, start Thunderbird in safe mode. - https://support.mozilla.org/kb/safe-mode

Does the problem go away?

Also see https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues#AVAST

I started Thunderbird with add-ins disabled and the problem did not appear. I then started Thunderbird and the problem appeared again. I disabled some add-is that I believed to be possible causes of the problem. and the problem seems to have disappeared. Thunderbird has been running for hours now and the problem has not reappeared. Thanks for trying. After I am sure the solution has been found, I will enable the disabled add-ins one by one to narrow my solution down to a specific add-in.

When I posted, I was mainly looking to see if anyone else had seen this problem and had already found a solution. I thought I could save some time in trouble shooting.

Sometimes the search does not find solutions maybe because I don't ask the question right or maybe because it just can't find the posted solution.

In any case, I thank anyone who has looked at this for me.

PhantomNum1 said

Sometimes the search does not find solutions maybe because I don't ask the question right or maybe because it just can't find the posted solution.

and sometime those that have found a solution have never posted what they found, instead just saying "I found it" so no one gets the benefit of their efforts except themselves.

HInt Hint for when you have a definitive result.