I have a 99 2500 and once I shut the truck off and it sits for like more than 5 mins and when I turn the key it takes like 5-7 seconds to start. It will roll over but just takes like 5 mins to fire up. But if I shut it off and come back before 5 mins it will start right up. And if I get home at night and wake up in the morning to go start it, it will start right up. What could be the culprit??