Is this a bad sign of a worned timing belt?

What is your question?

The engine makes a low grinding noises and stays constant. More noises when cold. No Engine light. The performance of engine is good. Once, the engine's idle went really low to 700 rpm like it is stalling. I accelerate the car, the idle returns to normal, noises also returned.

How long has your 1999 Saturn SL2 had this problem?

8 months