Will it only NOT start when you try to fire it up and the engine is already
warm/hot?

Pop the air cleaner off and watch the injectors during this no-start
condition.  Are they spraying fuel?

Doc

I'm assuming you have TBI. One common failure is that one or both of the
injectors leak. This results in 2 issues. 1. The fuel pressure bleeds
off overnight, and B. Fuel pools in the bottom of the intake manifold,
and sometimes trickles down into an intake runner. The symptoms of this
(depending on the severity of the leak) are Hard starting due to
flooding for short term restarts 1-3 hours, and Hard starting due to no
fuel after long term (overnight) restarts. Mid-term restarts usually are
OK. Remove the air cleaner, shut the motor off, and look down the throat
of the throttle body, the injectors are in the center on top. If you see
any drippage an injector is leaking.
KenG