Slow starting

[msvx95]

How do I know if my starter is bad? The car will usually start up 80% of the time on the first turn of the key...every now and then it just clicks and I have to do it a few times, but now my problem is this: When I start the car, it used to start up immediately...it's a sluggish start up and just seems like it's not getting enough voltage... Would my battery be the culprit or should I get a new starter? I'm puzzled...the more I try to start the car, the more it is sluggish...I'm worried one day that it won't start