With an automatic bid you indicate the maximum price that you are willing to pay for the lot. The system will automatically increase your bid if you are outbid by a third party. This continues until your aximum bid is reached.
It's not possible to delete your auto bid, but you can cancel it by placing a static bid at the amount of the next minimum acceptable bid

When another bidder places a static bid equal to the maximum of your earlier placed automatic bid, the automatic bid beats the static bid.