collapsed lifter? loose rocker arm? wiped out cam lobe?

[dbmx66]

so its been bothering me lately, i have a 84 k10 with a 350, real real mild cam. hydraulic flat tappet, somtimes when i fire it up, it makes a weird noise, its definitely in the valve train, but it doesnt make the noise all the time though, itll only do it every other day or so. i didnt get around to pull the valve covers off yet, but i was told its either loose rocker arm, collapsed lifter, or a cam lobe got wiped out, how do i trouble shoot this, i wasnt really trying to pull the intake and everything off right away. and one cylinder during the cycle seems to misfire, but not every time, so im confused on what to do. any help would be appreciated. thanks