When Firefox browser encounters multiple slow startups, the browser shows slow startup notification on how you can improve the startup time, that notification sends users to Refresh article on SUMO page. Here is the message in it with ‘Learn how to speed it up’ and ‘Don’t tell me again’ options at the end: ‘Firefox seems slow to start’.
FYI, this can be disabled from not showing in future if you’ve found it annoying. READ: Disable Slow Startup Notification in Firefox 21
There is a chance for that notification to be displayed to users, whose Firefox profile is quite new or a few days old. Then showing that notification, which suggests Firefox Refresh as a fix doesn’t help the user much when he is using a old machine.
Considering this, Mozilla has revised their decision and decided to show slow startup notification only when the Firefox profile is three months old and slow startups are experienced by the user. This change has been targeted towards Firefox 51.