Screenshots please, also any of the 'launch options/profiles' would be great specifically.
If you have issues with 'the game is already running' though, I recommend using task manager to 'kill' the already running game. I have come across similar before recently actually with a few issues with mods and the game not responding so I had to just kill it to make it possible to relaunch the game again. Me and mod testing to get a modpack working and that type of situation comes up. Sigh. This shouldn't normally happen though, but it should help for the most part even though it's annoying.
It should just when turning off the PC (meaning shut down, as well as ending the game with a save and quit/exit game, no sleep/hibernation mode type PC turning off, I assume you know, but I'm just covering possibilities that's all, nothing more) not have all that still in memory so no idea why that's happening unfortunately.