my service engine soon light comes on one one day but goes off the next??

[ben50520012000]

just bought my 96 geo metro 4cyl automatic with 106.000 miles on it,. allready replaced water pump and did timing ..the engine service soon light comes on every other day.. but goes off after driving a while.. it passed smog but just my a hair

it seems like the engine service soon light turns on in the morning when i go to work and says on when i go to luch but doesnt come on when i go home..

so that would be 3 start ups a day..

i dont have a haynes manual or ecm check tools... maybe its something easy?

thanks

[unbe]

I think I'd do a tuneup on it
Unbe

[ben50520012000]

just had new plugs wires cap and oil changed a month ago the light did not come on today very odd

[unbe]

Do you have a parts store near you that would pull the code for free?