Hi guys, have u guys ever experience something like jerk/lagging while playing some 1080p .mkv files???

ive recently gotten into 1080 .mkv HD movies, i have to say the quality out of most of the mkv files are the best for me.
But recently, i dont know is it because of the file i've downloaded or something, but when i play the movie, it somehow jerk/lag at a certain part of the movie for 1-2 seconds jerking/lagging.(when i repeated the lagged scene with different media players, sometimes is stil laggs at the same scene[lines appear n stuff], but other media player like media player classic do cut down the lag, but not everytime; as it still laggs at that scene)

May i ask does anyone experience these kind of situations? Whats the cause of this problem? Is is the media player im using, is not fast enough to cope up with the mkv file?? or is it someting got to do with my pc? graphic card/sound card all should be working just fine....hmmss?

What type of HD 1080p movies are currently the best recommended to download? by using what media player?