why do my apps need to “re-download”?

Apps show the little cloud and downward pointing arrow beside the app name. The app also is shaded and several will be in the process of downloadin. Happens at random times. if I’m not on wi-if I can’t download therefore phone is useless at that time until they download again. What can I do? I’ve included a Picture just to show in case my explanation sounds

And no I don’t have the “offload app” enabled.

Thanks