Engine backfires through intake on 2000 Dodge Ram Van 3500

Every several weeks my van backfires ( sounds like through the intake) Only does this when starting out warm.

Asked by for the 2000 Dodge Ram Van 3500
1 answer 2 comments
Mileage, engine,trans. and maint info all helpful to answer your inquiry.Any recent(3Mo.) repairs?
149000 miles.I think it's a 318,Automatic trans.No recent repairs, Has had regular maintenance.It did it about 6 weeks and 4000 miles ago than again recently. It lasts for about 30 seconds than runs fine again.
Thanks millions for any help.
Has the check engine light ever come on , or has it been scanned to see if any temporary (pending) codes are stored? maybe have 'live' data scanned to watch for misfires under the conditions described when it occurs.