This is usually resolved by cleaning the throttle body. Get a can of thorttle body cleaner and an old toothbrush. Remove the air intake hose from the throttle body and have someone hold the throttle wide open (engine off of course) while you spray and brush. You want to clean the bore and both sides of the throttle plate. Pay special attention to a harder black carbon ring that builds up in the bore just inside the throttle plate. Don't scrub too hard on the bore so that you do not damage the teflon coating.
You may also have a bad throttle body, but see if cleaning it solves the problem first. If not, see if the sticking is present with the throttle cable disconnected. If it is, the sticking is in the throttle body. Look to see if the throttle plate is actually digging into the bore. If so, the correct repair is to replace the throttle body although you can usually get by if you very slightly adjust the hard stop idle screw. Try turning it about 1/16th of a turn. Do not exceed 1/4 turn. Messing with the hard stop idle can throw off the throttle postion sensor setting and cause complications with the computer controls so do as little as possible while still solving the sticking.
The actual cause of the binding is usually that the throttle plate sticks or binds in the bore and is most pronounced when cold. As soon as it warms up a little or has been broken free, it probably seems OK until it cools down again. As mentioned above, this is usually just from crud building up in the throttle body.
