Have you tuned it up recently?--could be a bad rotor or cap,maybe they have a carbon track and shorting the spark to ground --if its damp or rainy it might do it more,then go away when its dry out--plug wires can do the same thing too...could be a hundred things,really..
You'll have to start by finding out if it has good spark in all 8 cylinders..often just taking the plugs out and looking at them will tell you if one isn't firing consistently,it'll be black and or gooped up with deposits..
It could be bad fuel,water in it,or the fuel filter is plugging up too...
Let's hope its something easy to fix and not expensive..
I have seen an engine run good for a day,then sputter and skip the next,clear out,run good again,and repeat the process,it turned out a head gasket was letting just enough coolant in one cylinder after sitting awhile,that the plug would foul...we didn't find that until we saw steam come out of the tailpipe the next morning,and it didn't spin right over as normal when we went to start it,it "stopped" when the piston in that cylinder went to go up,and it barely cranked,then sped up again and it started...then the steam came out of the pipe...pulled the plugs out,one still had green anti-freeze on it...head gasket was an original steel one that was rotted in one spot and leaked very slowly..
