I grew up first in a cult (a very controlling and frankly evil perversion of Christianity that collapsed when the leader died - it was later revealed he was sleeping with women in the congregation, taking money, etc, etc) but didn't really encounter speaking in tongues until afterwards, in the evangelical church my traumatised parents went on to after the cult collapsed.

Having been a Christian for some years (though I do not consider myself "evangelical" due to all the negative Trump-worshipping connotations of the term), my conclusion on tongues is this: Much of it is simply peer pressure induced mass hysteria. However, I have occasionally witnessed the real thing - ie someone inexplicably talking in Swahili, despite not knowing the language, and the translation turns out to be an encouragement or direction from God of some kind (from someone who actually speaks Swahili). Sounds insane? Of course. But tongues were meant to be a sign to unbelievers, as per the Day of Pentecost in the Book of Acts.

Outside of that, the apostle Paul encourages people who speak in tongues to do so quietly if there is no interpreter, since the whole church cannot then be encouraged by whatever the message might be. I have, on occasion whilst praying alone, spontaneously broken off into an unknown language for a few moments, only to then return to English. It is like something takes over. But this has never happened to me in public. Also, I have then discovered certain peculiar "coincidences" accompany the times I've spoken in tongues (for example, I may have suddenly had an urge to pray for a friend who it then turns out was in serious trouble of some kind at that precise moment).

That is my experience of tongues, more or less. There is a lot more I could say about the Holy Spirit and how I believe he speaks today, but that's another discussion. :)