Apple Watch Screen Size

From time to time the screen image on my Apple 4 watch gets so large I cannot see it all. It is also so large that I cannot even sign in with my passcode. This is happened many times for no reason and it normally goes back to the normal screen size over night or after a few hours. I don't know why it's doing this and now it is stuck in the giant size and I can't use the watch? Any ideas?