To my knowledge, Firefox doesn't do any different kind of clean-up when you restart your computer compared with when you close and restart Firefox in between Windows boots.

If the problem is limited to Windows restarts, I suspect that some external software might be involved. For example, software that cleans up personal data or software used to "sandbox" your browser so that it can't store settings directly on the hard drive. Do either of those sound like potential factors on your system?

Do you know what the IOBit Apps Toolbar extension is for? One description I saw in a search was some kind of adware. If that just showed up recently, it could be that some "free" software you installed includes unexpected or unwanted components and may be affecting Firefox. At a minimum I suggest disabling that extension here:

orange Firefox button (or Tools menu) > Add-ons > Extensions category

You might consider making additional backups of your settings folder. This would capture the last state of your history/bookmarks file (places.sqlite) and open tabs (sessionstore.js) so that if necessary you could restore them. Depending on what is clearing these files, you might need to store them externally (e.g., on a USB flash drive or in cloud storage). These might help:

• Back up and restore information in Firefox profiles
• https://addons.mozilla.org/firefox/addon/febe/ (for latest version, see the versions page: https://addons.mozilla.org/firefox/ad.../versions/) (I haven't tried this add-on myself)

Thanks...you reminded me that I had Advanced System Care that is running on my computer and that it does Automated clean-up. It appears that even though I had adjusted it so it did not wipe out history and downloads...etc. Somehow, it reset itself. I have readjusted and now it works again. thanks