Why does Vishnu lay on a snake?

Question: Why does Lord Vishnu choose to rest on “sesha naga”.

Sesha Naga is an expansion of Lord Vishnu who assumes the form of a snake for the Lord to rest on. The snake is a representative of time. Sesha means “what remains” or “balance”. In the Lord’s lilas, all the related paraphernalia is a form of His expansion as Sesha. Thus everything, from the Lord’s bed to His umbrella and shoes, are all Sesha. Why Sesha takes the particular form of a snake for the Lord to lay on is because a snake represents time; and as the controler of time the Lord is situated beyond it. This is shown by the Lord laying on a snake.