Starters are shiny locked in sword and shield which means that you cant get them at the beginning by soft resetting you would have to get a breeding pair or a ditto. Preferably I would go with a ditto from another country so you can do the Masuda Method.
I used this in Sun and Moon. Matsuda is best for SwSh. Or KO the same thing over and over.
Shiny charm, shiny foreign ditto. Masuda meathod.
Try your best
Three day skip in raids
Trade for a Foreign Ditto and breed. Otherwise know as Masuda Method
It honestly depends on what method if ur going for a starter the usual method would be to save at a point before u get ur starter and choose the starter u want shiny if not shiny then restart the game and try again but most pokemon is honestly based off luck u can increase ur luck by getting a shiny charm after u beat the game which shiny charm is post game. Thats the only info ik tbh
Go outside xd