Knocking at Startup

Hey guys, I have an '07 JK Sahara, all stock. About 75k mi. Recently started a slight knocking at startup. Runs fine, just a little knock for about a second or two at start and will only do so after sitting awhile (over night, at work, etc.). Bought used at first of the year, have an extended warranty but just troubleshooting ideas to see if its a quick or easy fix before I take it in and have to pay the deductible and/or diagnostic.

Sorry if this problem has already been covered in another thread, browsed through and didn't see any.

Someone more mechanically inclined will give you some pointers to look for.
I'm not that person.

Some basics to try...

1) Check your oil. Low or gummy can oil lead to knocking. If it's really black, you need an oil change. I'd put some seafoam additive in your oil a day or two before you get it changed and drive it around. It should help to clean it out your engine.

2) Check your air filter.

If it does it after it has been sitting for a while, I bet it is the oil filter. I had bad luck with the Fram filters, I would get a dry start every now and then if the jeep has been sitting. Either stick with the Mopar brand or I have had good luck with Mobil 1. The JK's filter is horizontal so sometimes the oil can drain out of it.