As depicted in the trilogy:

• Sauron did not lead his army to Minas Tirith
• He did not defend the gates of Mordor from Aragon's army

In fact, he was never physically involved in (any) battle ever since his duel with Isildur. In spite of noticing Frodo and Sam near the mountain of doom, he never really comes out (physically) to block them from destroying the ring.

Was he limited by his physical condition or he was not willing to battle without the ring? What was the reason?

As depicted in the trilogy:

• Sauron did not lead his army to Minas Tirith
• He did not defend the gates of Mordor from Aragon's army

In fact, he was never physically involved in (any) battle ever since his duel with Isildur. In spite of noticing Frodo and Sam near Mount Doom, he never really comes out (physically) to block them from destroying the Ring.

Was he limited by his physical condition or he was not willing to battle without the Ring? What was the reason?