Sounds like a possible IAC valve going out. I'd want to check the Idle Air Control (IAC) valve with Consult II to insure that it either responds correctly, or fails.

Also, could be a Mass Air Flow (MAF) sensor going out as well.

But, this is stricly conjecture, as I'm not there to see the little things (massive sucking sounds when this happens? erant spark noise? A/C compressor on due to defrost being on? Battery condition? Alternator condition? MIL light on? etc...).