1994 Jeep Cherokee Check Engine Light

I have a 1994 Jeep Cherokee 4wd, 6cyl 4.0L, 120,000 miles. I bought it used to have at a remote location and it is used intermittently at best, monthly. When I turn it on, the check engine light comes on. If I drive for even as little as 30 seconds, turn off the engine and turn back on, there is no light anymore. I just learned about getting codes, and will not be able to check them for about 2-3 weeks.
I was wondering if you have an idea of what it could be. I figure it has to do with the period of non-use. Why the question before the codes? Next time I go to it, I'm going to change the oil and probably the air filter, and I'm wondering if there are other likely culprits that I should replace, too. Any opinions? Thanks.