[bobcowan]

In my experience, ignition problems usually manifest as a complete failure. The engie just quits, like you turned off the key. Some components (like the coil) will gradually fail, and the engine runs poorly. But that is usually consistent as the component heats up.

Fuel problems usually manifest like you describe. They can be intermittant. The engine sort of dies out, coughing and gasping. Playing with the throttle can bring it back, or prolong the process.

I would be looking for a fuel problem first.