2002 Buick Rendezvous slow start

The starter could be drawing WAY too much amperage. This will cause it to spin slow and eventually, it won't start at all. It'll just click. To check this, you'll need access to an electrical system checking device. We have one at my shop. It connects to the battery and has an amp lead that clamps around the positive cable from the battery to the starter. If you are able to find this type of tester, the amps on a good starter should be about 175 to 225 amps. If it's approaching 300 or more, the starter is drawing too much amperage and needs to be replaced.