No Start

My starter is going, but it doesn't get the engine going. Most times it happens in the morning or when I don't run it for a while. If it don't start in the morning, I can come back in the afternoon and it starts just fine. If I keep starting it and it don't start then it gives a rough idle so I have to rev it up until the idle becomes smooth. This been happening off and on for couple weeks. What can it be?

Oh sorry. I have a 1998 Toyota T100. 3.4L engine. 5-Speed Manual. 4 Wheel Drive. Approx 156,000 miles on it. Timing was last changed 77,000. I changed the Sparks (NGk Iridiums).

The engine cranks over but does not start and or rough idle? But starts OK when air temps higher in afternoon? How does it restart if the engine is hot?

once the engine is started and ran trough, i can turn the engine off and start it up again and it starts up just fine.