Was just sitting in the drive-thru about to go on a 3-hour trip and I noticed the idle would dip down to about 500 RPMs then recover to a little over a thousand. Then it would settle down at 750 or so again and repeat this process every 5-10 seconds or so. Currently on the highway and all seems fine. No check engine light or anything. What should I be checking first? I'll be limited on tools for a weekend getaway so hopefully it only affects idling.