I just created account here, so I searched for open issue but I was a bit overwhelmed so I created a report. My Nintendo switch has always taken a while to boot minecraft, on my account, my wife has one on the same device, hers loads fine. My daughters both have their own Switch device, no issues there with loading.

My account is the owner of our Realm, this is where I believe the issue is causing problems. Recently(past month), minecraft 'had' become unplayable on my account, due to freezing, it happened on menu's, click a button, like play on title screen, you see the button down graphic, but no sound, then, no buttons or navigation controls had any effect, Froze! Same would happen playing in realm, open a chest or try to open craft menu, I could walk around, but no menus, chests, options would ever open, and I could leave it, it would never kick me or start working again. 

It got so bad I started using my wifes account just to play, even had to get Android PE, to maintain realm. 

I'm sure there is an open report, sorry for not finding it! I "Fixed" the issue yesterday, in the Data Management there is a option to backup to cloud, and it has a toggle for auto back up to cloud, it was turned on, by default I'm assuming since all three devices had the auto turned on. Once I turned it off, it hasn't froze since, before it would take an hour and 3-4 software reboots to actually get to the realm, after, I had 30 min tops before it would freeze. Looking at the information from the backup option menu, it seems the Nintendo was attempting to BACKUP MY REALM, I have one world on my device, a redstone testing world, 5 mb file size, and the backup utility was trying to back up a large file, and never completed more than 3%. 

I hope this helps someone, certainly Mojang, but once turning off auto backup to cloud, I've got my GAME BACK!

PS: We should be able to access the contents of a shulker box from within the UI of the containing chest, especially the Ender Chest, at the least. JS.