Try some bot games and see if it still happens; is it just the anxiety of playing on summoner's rift, or playing other players on summoner's rift/playing in normals? Some players (especially in normal games, which I find just flat out strange) take this game way too seriously; I know I encountered some seriously toxic people when I was still leveling up. I find there are actually fewer toxic players in mid-silver ranked and in bot games; there are a lot of toxic players in the lowest ranks (probably why they're in the lowest ranks) and in normal games (again, what the heck? lol). Sometimes you just need to make friends with the mute button.
I still get some pre-game jitters when I'm getting ready for ranked solo-q, but focusing on the game/having things to focus on helps me feel less nervous. Really though, the outcome of the game doesn't matter, your KDA doesn't matter, and your own performance doesn't matter unless you want it to. I choose to focus on my own performance, making sure I'm making good decisions, that my mechanics are good enough, that I have adequate game knowledge and map awareness, etc. Even if I lose the game, or get crushed completely, I can still learn something, which means every game, win or lose, I accomplish something. Don't beat yourself up over mistakes you make, everyone makes them, including pros, and you can learn from them. In a lot of ways, losing a game is more useful than winning.
At the end of the day, this is a game, and you're supposed to have fun. Some people enjoy the competition of ranked play on summoner's rift, others like to goof around in other game types. It's really up to you what you want out of this game. You're still only lvl 23, so you're still learning the game; don't sweat it. Honestly, I don't think most people learned how to actually play the game until they're well after lvl 30/ playing at silver rank level (you get some bronze players who really should be higher ranked, and some silver players who probably got a lucky streak/elo boosted or something). GLHF :D