In particular when watching the show on television it is never evident what episode starts playing. Is the episode title displayed at any point during the intro or credits?
It doesn't... usually.
In the vast majority of Simpsons episodes, the title is never shown on-screen. It is contained within the TV listings, so if you press the Info button on your digital remote, it will display the episode title along with a short synopsis. Each episode's closing credits also lists the episode's production code.
There are, however, a few exceptions to the rule, the primary ones being the annual Treehouse of Horror episodes: each one has its own title card, and a title card for each individual segment. Episodes that parody other shows - such as "Behind The Laughter", a parody of VH1's "Behind The Music" - also tend to have title cards based on whatever it is they're parodying.
The Simpsons Wiki has a full list of episodes that have title cards, as well as screenshots of said title cards, and notes that out of over 600 episodes:
The only canon episodes with on-screen titles are "The Telltale Head", "Bart Gets Hit by a Car", "22 Short Films About Springfield", "The Book Job", "Homerland", "Barthood" and "The Great Phatsby: Part One".
The latter four, like "Behind The Laughter", appear to use their title cards for parody purposes.
Like most shows, The Simpsons did not typically show the titles to any of their episodes on TV itself, with a handful of exceptions including the annual Treehouse of Horror episodes. If you wanted to know the episode titles in the pre-internet era, you had to look it up on a TV guide.