Wither makes game unplayable

After spawning the wither, the battle was pretty easy since I was using my bow. Until it reached half its health. The game basically lags up to the point where it might just crash the game out. Each time I get near the wither, it just lags to no end, only until I get away from it it stops lagging. I really want to know if this is just a game thing and my switch is to blame or something because it's somewhat fairly close to my town and i don't want to risk it coming over and destroying everything.