_gonzo_

OK, the more info the better...

If it was in full sun and too dry, or shade grown or any combination thereof:

Try and keep it in good light or even in filtered sunlight but, not direct sun. If you cannot do that, keep it indoors and gradually reintroduce it to morning sun only as the next best thing once it recovers. This plant does not want to dry out (completely) either so keep it moist but not sopping wet. Do water whenever the soil feels like it is drying but, also make sure the pot is draining well.

If it was exposed to too much cold weather:

You would get a similar reaction. So try and protect from cold as well if it applies.

If it has been newly repotted and the root system disturbed and then placed in full sun:

Even morning sun now is not advisable for some weeks depending on recovery.

For the coming weeks do what you can to keep it damp and protected. If it is not too far gone, it should show signs of new growth soon.

Finally, just so you know, if it were over watered as you initially thought, the leaves would have started to turn dark brown or almost black instead of yellow.

Good luck to you.

Cheers,

_gonzo_