I have a 1993 toyota corolla automatic. It keeps stalling when at a red light or just at a stop. I already took it to the shop about 4 time already but it seems like the problem wouldn't go away. Also, when I change the gear to park to drive it seems like it not aw smooth. What causes the stall?

thank you!
Also, before it stall the engine kinda shake and it stall...I hope this additional information can help...