Start up/Wait light

[dan385]

3 times in the last month I''ve had an issue with start up. After running my Humvee for 20 minutes or so and then trying to start it again an hour or so later, I turn the key on and the wait light doesn't come on. I wait a few seconds, try to start it and it turns over but doesn't start. I wait between an hour and overnight and it'll start again. It's never done it when the truck's been sitting for several days, starting right up without issue. I looked at the protective control box...it looks pretty new. Anyone had this issue? (1986 M998)