I have had a very similar problem with my '00 SVT. It turns out that the starter was going bad. I replaced that and haven't had any problems yet. My symptoms were the same as yours, good battery, no crank. It would only happen occasionally. I am thinking that this might be the same problem as you. If your is a MTX try to push start it when it is having the problem, that way you won't be stranded anywhere. I hope this helps.
