Try this:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste tracking and pause while the list is filtered

(3) Double-click the privacy.trackingprotection.introCount preference and increase the value above 20 (the maximum number of times you should see the tracking protection tour is 20)

Does that help? Does it survive your intersession cleaning?

Hello and thank you to answer me.

No, it doesn't matter. privacy.trackingprotection.introCount reset to zero, so it immediately returns to 1, and then to 20.

I even tried to erase the value of privacy.trackingprotection.introURL, but nothing.

The problem is with the new version of Firefox 49.

Kind regards.

I haven't seen it recently, so I don't know why yours feels the need to keeping showing it. ??

Hello and thanks for your help,

I ended up finding. This comes from my user.js file

In prefs.js and user.js privacy.trackingprotection.introCount did not have the same value, whenever I restart Firefox the problem reappeared.

Kind regards

Good idea! For anyone curious about what a user.js file is, see: How to fix preferences that won't save.