Engine stall while driving

Engine Performance problem
1997 Toyota Camry Automatic 100000 miles

For about a month my car has been doing weird things at stop lights when I am idling. It is almost like I am not pressing the break hard enough or something; sometimes the car just lurches forward a little bit. Also, the car will sometimes feel as if it is going to die, then when I press the gas, it won't go for a second, then goes all of a sudden. Last week the car actually did die at a stoplight, it just turned off and it would not even try to turn over, there was no sound from the engine at all. I just got the battery replaced so I don't think it is that. Then about 15 minutes after that happened, I tried to start it and it started fine, but by that time a tow truck was already on the way. The mechanic I took it to said they could not figure out what the problem was, but obviously there is a problem!
Any ideas?