it is the flasher/turn signal (blinker)oscillator (same part). The cost of the part is $25 from GM online. I need to perform the same service and am waiting on a good deal for the complete 3vol Intrigue service manual. Try engaging the cruise control button on - this seems to help the situation by providing more power to the oscillator. I keep toggeling the flasher button (my flashers (hazards) will sometime stop also) until I get the flashers to flash for about 20 time straight with the flashers on, test the blinker, repeat until the blinkers start to work again. (the hazards are held on until 10-20 straight oscillations and then turned off to test the turn signals).
This is a circuit board (of the flasher/blinker assembly) problem because of shoddy soldering craftsmanship. In the heat the material expands and the contacts get worse. Cold=contraction better connection. The problem will get worse and worse as the part expands/contracts further worsening the solder contact area.
Pontial Grand Am, Alero and others have the same problem. Some problem on other GM parts like the Truck wiper assembly. Shoddy soldering. You may be able to resolder the part. Sometimes due to corrosion (usually a surprise) also.