218k miles. Your hybrid battery may be on its last legs. If the hybrid battery is low, the ECO light won't turn on as the car is operating in a different mode, using the gas engine to keep you moving, but without taking full advantage of the hybrid system.
You need to have you hybrid battery tested by the dealer or a reputable shop that specializes in hybrids. Very likely, your hybrid battery is due for replacement, as >200k miles is a reasonable lifespan.

 

Despite what others have said, your battery is not on its last legs. This happens with my car too. It's because if you go into neutral with the battery already low, the engine can't start up to charge the battery, so it runs the battery down really low from sitting. As for the ECO light, you probably accidentally turned off ECO mode, the button is below the shifter in the center console.

 

It's because if you go into neutral with the battery already low, the engine can't start up to charge the battery, so it runs the battery down really low from sitting.

This is NOT correct. The car needs the hybrid battery to start the engine. It can't start the engine with the 12V battery alone. The 12V battery is only used to energize the main power relay and from there on, the engine is started by the high voltage battery (using MG2 in the eCVT as it doesn't have a 12V starter). For that reason, the computer never allows the hybrid battery fall below a certain level and starts the gas engine before hybrid battery level reaches certain minimum. If the hybrid battery charge falls below the minimum level, the car is basically bricked, because it can't be jump started like a normal car.