Yesterday I got in my blazer to go home from my buddys apartment. I turned the key but the truck didnt even try to crank. I thought the battery might be dead but the lights came on and the stereo came on. Crawled under the truck and tapped the starter and the relay a few times with a rubber mallet. I then had my buddy crank it and it started right up. Since then I have started it several times with no problems. So is my starter dying or what?