Maybe this is why Carey Mulligan split with the Transformers star! Shia LaBeouf decided to block a couple's car with his massive truck in Studio City earlier today - when the couple returned from shopping Trader Joe's, they had to wait 40 minutes for Shia to finish eating lunch at La Salsa...

And after a security guard questioned Shia, the young actor didn't even offer the couple an apology. Lame! Watch the whole thing play out above.