weird sound on cold start

I own an '07 GT with just over 100000 miles and I have about 3000 miles on Mazda Reman. I have noticed in the past week or so that on cold starts I get a weird high pitched sound when idling and it disappears when I push in clutch pedal. I have not noticed any performance changes, just this weird sound that disappears when I push in clutch. I only noticed it happen a couple of times in the past couple of weeks.

Any ideas on what it is? Is there a fix??