does this happen after freezing the app to ram and than reentering it? what phone is it? does a full closeout and reentering of the app solve it?
is this over a mobile hotspot? if so it might be related to
MCPE-43588 (my issue)
ive only seen this in games with broken skybox implimentations what gpu do you have and are the drivers up to date
judging by all the reports here it seems there are performance issues on the switch with the latest update in the mean time until its fixed you can turn down the render distance and/or turn off fancy graphics and smooth lighting
duplicate of
MCPE-43588