What codes?

My first thoughts are air/vacuum leaks... would check fuel trims to begin with...

Not one...ever.
To be so intermittant I just cant see it being a vacc leak.

I had the same problem with my 06 STR which occurred about 4/5 times a year. Always when driving at walking pace (usually in traffic jams) and always when the car was fully warmed up. Sometimes it didn't actually stall, but you could see the rev counter dip very low before it "caught".

Seemed to go away (keeping fingers crossed, has been about 12 months) when I had my brake servo replaced (which had failed completely - was obvious when I had a loan car one day while mine was in for a new header tank). I'm guessing it was causing a vacuum leak.

Pending codes will appear and disappear, and of course no MIL, if it's intermittent but would be worth reading. If you can catch it, fuel trims in normal use as a baseline compared to when it occurs may tell you what is faulty but really intermittent things are tough. It can be anything from a chafing harness to a split pipe to a sticking valve.

Chafing harness can be found by wiggle test if you're lucky, but there's little wiggle room on an STR.

If it's vacuum related, with the car idling, get a spray bottle with soapy water and start spraying around any and all vacuum lines. Connectors, wires, etc.... This should pin point the area and help you find the problem. Providing its vacuum related