W202 stalls at idle

Hello all:

96 C280... runs great but I have an annoying problem. When cold, the cars starts perfectly, however, when hot it will start normal then stall if left at idle about 5-10 seconds later. It will restart again quickly, but the cycle will repeat. If I rev it up a little, at that 5-10 second later mark, it will hesitate for a sec, then will run fine. Took it to my regular mechanic, he is very good, but apparently bought a castle and now he's charging ridiculous amounts of money, said it was probably a relay. No error codes at all. Apart from that the car runs great. Any ideas which relay should I troubleshoot?

Thanks