the side window on my 2005 Dodge Gran Caravan some times don't go down or up

Sounds like you have a weak window motor. Eventually it will stop working. If you like we can look at it for you on Monday

As a 'temporary' fix - try spraying liberal amounts of silicon lubricant into the both window guide channels to see if that helps.... Silicon spray lube is available at most any parts store or in big chain retail - hardware. (Agree with East Bay Auto)