If I quit from a world/server and rejoin one my game makes random blocks appear + dissapear

Put the summary of the bug you're having here
I load up minecraft. Nothing wrong wrong with it whatsoever. I quit a world or a server and join onto the same or new one. It makes blocks disappear and reappear randomly. When I open my inventory massive silverfish-type things slide across the screen.
What I expected to happen was...:
Describe what you thought should happen here
Me to rejoin and not get that happening.
What actually happened was...:
Describe what happened here
I rejoin a server then blocks start to dis- and re- appear in random places.(never in about 10 block radius of my player.
Steps to Reproduce:
Put a step by step guide on how to trigger the bug here
1. ... Join a world/server
2. ...Leave the world/server
3. ...Join a different world/server.