Dryer vents are one of the leading causes of house fires. If they are short through-wall vents, maintenance is fairly simple. Slide the dryer out so you have room to work. Disconnect the flex hose from the wall. Slip a dryer duct brush through the duct and out the other end. This should be inspected annually and cleaned as necessary.
If your duct runs up through the attic and out through the roof, you’ll probably need a professional to clean it. These are even more troublesome as dryers are not built to move air through a long length of duct.