What year is your car? if it's 90-95 see if there are any OBDI codes. If it's a 96-12 an OBDII scanner will work. You don't always get a CEL when you have codes.
Last week I took the family on a trip for a week. As usual, we took the wife's car and my Miata sat in the garage. When we got back I was getting my Miata out of the garage but it wouldn't start. It cranked over fine but had that out of gas sound to it. The battery seemed strong so I cranked and cranked and pumped the gas pedal (was I thinking it had a carburator or what?). It slowly came to life and ran good. What would cause this? It uually starts and runs great when I drive it work M-F. It has no mods. New spark plugs, wires, fuel filter, TB, water pump and all hoses. 150k miles. My next trip will be a week in Oct. Should I expect it again?
You might wish to check the fuel pump pressure, just to take that possiblity out of the mix.
How old was/is the gas in the tank? My Miata sat for months and I was still able to hop in and crank it over once a week. I did notice the more it sat the worse it ran eventually to the point of a miss at idle and almost NO power anywhere in the rev range. $2.99 can of Berryman's B-12 Chemtool cleaner in (with a fresh tank of gas) and a nice spirited drive cleaned it right up. Car runs better now than it did before I parked it! Idle is smooth, and engine screams up to redline now. Just an idea. :)
Oh yeah, it's a 1992 with the stock 1.6. I figure if I drive it 78 miles a day, it gets plenty of gas run through it. I know the fuel pump is turned on by the air flow meter. Is it possible that the vane is sticking closed after sitting for a week? Then again, the engine would have enough vacuum to move it open. I'll check the codes.