Normally the cause of this is an expansion valve that will not open up fully because it is stuck. Your system looks like the second link that Paulster2 linked. The valve is way under the passenger dash and really painful to mess with.
If you can't live with it as is, I would ensure there is sufficient freon in your system (probably is based on blowing cold initially). Then assuming good freon level, discharge the system, replace the accumulator/drier cheap 20-30 bucks, possibly clogged, and easy to replace. It's just behind the driver side headlight, swap old for new and then vacuum the system and refill with freon; cross fingers that it works now. If not, the next step would be replacing the expansion valve, which is a pain and not likely something you want to attempt yourself.