I have a 2011 j/k ur with 25000 miles on it. Just started making this grinding noise on start up only after sitting over night. It only does it on first start up. it won't do it again unless it completely cool off. Just started doing it about 1000 miles ago. I think it would be to early for the starter. And the oil levels are good. So what else could be the rough start. Hard to diagnose being its just an initial start thing. Has anyone else had this problem?