Almost every single Zelda game starts with Link waking up. BOTW - he woke up in a pod, SS - It starts with a dream (or nightmare) and he is awoken by a loftwing. And of course, many other games including the 2 and 3 dimensional Switch, Wii and DS games. Of course it could just be there to be funny, and I could be being over analytical, but it could symbolise this : The Hero's courage is awakening inside him. In certain Zelda games there is a known "hero" or "hero in green" but they don't always straight forwardly mention Link, this particularly is demonstrated in Phantom of Hourglass. This could show that there has been a hero before Link, or a reincarnation of Link and Nintendo may be referring to the previous games in the Zelda series. The colour green, the colour of Link's signature and yet classic outfit, symbolises renewal. This supports the fact that the "hero" before was in fact a reincarnation of Link and once he has saved Hyrule and defeated evil, he goes back to sleep and wakes up to a new start. It seems uncharacteristic for Link to just be sleeping in where he is a hero and has to save Hyrule from evil. This dream could just happen to start off with the cliché, waking up. He wouldn't rest until the Triforce is safe, Ganon/Ganondorf/Calamity Ganon is defeated and the last Metroid is in captivity. If Link was dreaming these, it would explain the familiar themes and places, and why the history almost repeats itself. Maybe every time Link wakes up, its an indication the previous game was a dream.