The Elizabethan wheel of fortune is derived from the Medieval wheel of fortune, which in turn was derived from the Roman goddess Fortuna and her wheel.
The essential concept is that we are all on an ever-turning and often unpredictable wheel of fortune, which moves from good luck to bad luck to good luck to bad. Today, we may be at the top of the wheel, riding high, but tomorrow, the wheel could turn so that we are at the bottom, having lost everything. Fortune's wheel in the Middle and Elizabethan Ages was wedded to the Christian idea that the present world is temporary and unstable—not to be trusted in. Fortune's unreliable wheel revealed to people that they should keep their focus on heaven.
Shakespeare makes use of wheel of fortune imagery in more than one of his plays. For example, in King Lear, when the Duke of Kent, whom fortune once favored with power and prestige, ends up placed in the stocks, he says:
Fortune, good night, smile once more; turn thy wheel!
By this, he means his luck has bottomed out: he knows, however, that this can be a temporary state, so he cries out for better luck to come his way, envisioning it as a wheel turning.