Hi I recently bought a used 1999 C280 with 55K miles. I have driven it for around 400 miles now. Recently while waiting on a traffic signal the car just shut down and all dashboard lights came up. The car was in "D"rive gear and I had pressed the brake while waiting. I restarted the engine after changing the gear to "P"ark. It was a long start and I pressed on the gas to get the engine going. This has happened twice, once with AC on and once with AC off. Also, both times I had travelled around 4-5 miles and the engine was at above 80 degrees temprature... which seems pretty normal. After I restarted, the engine seemed to work pretty normal. While waiting at traffic signals (in "D" mode with brake pressed) the RPM of the engine is around 600/min and while on the "P"ark mode it is around 750/min.

Can anyon guide me if this is a common problem or a serious problem. And, how can this be resolved?

Thanks in advance for your support.