I would suspect you have a defective sail switch. This switch must be open before the ignition sequence and closed afterwards. (Or the reverse, I forget) Putting your hand over the outlet changes the air flow which giggles the switch into working one more time.
They are relatively easy to replace (After you finally get the furnace out of the rig). Download the manual from the manufacturer.
My wife and I would travel full time, but we have to sleep occasionally.
2001 Tiffin Alegro Bus 40 ft DP named the Wild Eagle
Followed by the Eaglet - A 2005 Jeep Grand Cherokee.