'98 QX4 sometimes won't start, stalls suddenly while driving

[RCosta]

Most of the time, my 1998 QX4 has been rock-solid. I'm having an intermittent problem, however, with engine starts, and stalling--the latter most recently at highway speed, when the engine suddenly quit.

Originally the issue involved starting. It usually starts up immediately, but when it doesn't turn over the first time, it can take from 5-15 minutes before it does. No codes are being thrown. I initially replaced the battery, then the MAF sensor, had starter checked (no problem), and yesterday, changed the fuel filter. The latter apparently hadn't been done in quite some time, and the QX4 ran great throughout the day.

Last night as I was returning from work, it just quit again as I was driving; no warning, as usual. Was able to get to the side of the road, but then it took an hour before I could start it again so that it ran (it did start several times, then promptly quit, until once it didn't). What's my next step? Any help would be greatly appreciated.

[Towncivilian]

Welcome to NICO!

Check for excessive dirt or dust buildup under the distributor, and check for excessive scorching.

[RCosta]

Thank you much and will do, Towncivilian!

[RCosta]

Unfortunately, this didn't solve the problem. It's happening a bit more frequently now, and when it fails to turn over the first time, I've noted it's harder/takes more time to get it to start in the evening than the daytime.