Does this sound like air in fuel system or something mechanical?

It has been "surging" for some time when idling or stoped at a light but I let my '84 C-10 sit for 5.5days and cranked it up this morning. It fired up immediately but then the engine started reving up and down and it died. I let the glow plug cycle again and I crank it for 5 seconds and it acts like it is trying to fire. I rest the starter for 10 seconds and try again after glow plug cycle. Another 5 seconds of cranking and it fires up and runs super smooth and seems like it has a lot more power than normal. Anyway, it did the exact same thing 5 hours later when I went to lunch. Any thoughts?

fuel filter.

doesn't sound like an air leak. if it were, after sitting overnight you wouldn't be able to get it started again without bleeding the fuel system.

thats my .02

x2 on the fuel filter.
My dad had one with an airleak and it wouldn't start after sitting for the night. Putting an electric fuel pump on it helped. Now that I think about it, I'm not sure he ever found and fixed the leak :p: