OK i kinda blew it off the first couple times I noticed it but now its become a regular thing. Every time I turn the ignition, for a split second (probably on first spark) the truck makes a slight dieseling noise but only for a split second. after that, she runs fine. Idle is perfect, power is what its always been (a little laggy but I need to give her a tune up next month). Any ideas?

Addition: Also, i noticed since it got cold outside, the "service engine soon" light is coming on intermittently. Sometimes as soon as I start the truck and it'll shut off in a min or two and sometimes its on for 2 days then shuts off.