Uncanny commonality with 70s candid photography portraits, derpy young people exploring their self-presentation in front of a mirror & early digital selfies.
Unfortunately not. It isn't an area I paid much attention to, besides enjoying the images, and my memory now is awful besides.
You'd see a bit of it on album covers from the 1970s onward, as well as pop/rock magazines, the odd Time magazine cover & some movie posters, so if you can explore that you should start to uncover photographers you could look into further. Also portraits taken of US soldiers by people who went to document the war in Vietnam.
There's bound to be some art historians whose work is primarily on self-portraiture, whether as an overarching topic, or focussing on specific subsections such as digital selfies made since the advent of the smartphone. If you can rummage out some papers or books on portraiture, you should get some good leads & from there narrow things down to people researching the stuff you're curious about.
The first category I mentioned are mostly not self-portraits, but share a lot in composition & expression. The second mostly go unrecorded... and yet some are, whether by the individuals or by their friends, but have seen a bit of it from photographers interested in documenting such explorative play. The third are mostly scattered about on people's devices & websites, but again, some will have passed into more formal contexts.
Guess if I had your query, I'd spend an afternoon browsing record shops, and both the art & the history of art sections of a book shop, grab some names & go from there. If I were contemplating whether it could be something to work on as a thesis, I'd skip directly to emailing the National Portrait Gallery in London & asking for tips - it is a wide question but they'd have more useful general pointers than I could ever give.
Thinking about it, there is a good deal of earlier portraits & self-portraits swimming around in my mind now, which likely inspired the stuff am thinking of, but they're not part of the defining style of their eras. Again, struggling to summon names or other details to give you.
