Same issue here. Game is basically unplayable as it stands. Opening chests, trying to cycle through the hotbar quickly, and autosave all cause lag and/or freezing for 30+ seconds, sometimes as long as two minutes. And this occurs at least every ten minutes, sometimes within two or three minutes of each other.
Adding a second comment to back up theories regarding mob spawning and freezing/lag.
Whilst in an area with no mobs spawning I had intermittent freezing but it was playable, and irregular. Then, whilst doing some work slightly below ground, I heard a load of mobs spawn above me (skeletons, spiders, and witches), and the game is now freezing every few seconds. I've had around ten minutes of playable game in the last half hour or so.
In my diamond strip mines, there is barely any lag or freeze, and they are way below any spawnable areas.
Played on Switch, 150ish MB file, offline, survival, normal difficulty.