turn signal problems

i have a 99 grand am se i have a problem with the turnsignals the y will work fine and then they will flash really fast the next time and then they will work fine again and then they flash twice and stop when you turn off the car they will work fine again any suggestions would be great ly appreciated had it back where i bought it and they say there is nothing wrong with it

Looks like you may have a bad socket or bulb. When it starts to flash fast, look at the outside bulbs and see which one is not flashing. replace that bulb and/or socket for that side.
Good Luck.