"Should I Start Ranked Now? "
I don't know about doing it now, having that as the question here. Tahm Kench is new and Devourer can throw things into Crazy at the moment. But it's whatever; if that is something to consider or not is up to you.
To the main topic: I believe you have been given some misleading notions about what Ranked is. Ranked is a mode where your wins and losses are recorded and given an LP number that raises and falls so that a player can track their own progress with a goal of improving their own play. That's really all, it's not the end game of League of Legends or anything like that. It's just a different queue of the same game on the same map that is (intended to be) a pseudo-competition environment. Go ahead and play ranked if you want to or go ahead and don't; the majority of players in League don't.
"I've heard lots of stories about ranked games, that they're bad and people flame a lot and there are more trolls there than in normals....or just keep on being trolled etc."
That's true to some extent. Being a queue that is supposed to simulate competition and where "your losses matter", people get more stressed and flaming happens more. I can tell you that all of my experiences with "top laner feeds 3 kills and ragequits" have happened in Ranked. And as you can see from these boards, there's no shortage of people very eager to tell you about their trolled game.
"I'm worried I might become Bronze 5 or 4 and never get out again"
Don't be. Like I was writing above, Ranked Queue is like a High Score board on an arcade cabinet. Your wins give you points and you try climb up it. A person shouldn't play out of worry that the won't get one of the top scores in Donkey Kong or Time Crisis; people can still enjoy it. There's nothing wrong with being Bronze. The majority of people who play League don't play ranked, and of the ones who do, the vast majority of those players are Bronze & Silver. There's nothing wrong with having normal play at a game you enjoy.
"and never get out"
And let me tell you something about those "You can never get out of Bronze" ELO hell guys. They always blame and bash their teammates saying it's their teammates fault they keep losing but if you look at their play, their matches, you can see that's not the case. They blame the all the feeders on their team for the loss, but their teammates didn't make them take AD masteries on Vladimir.
