Black05lariat

my 05 sometimes bogs down when im pullin out from a redlght or turnin onto a highway accelerating. it doesnt do it all the time but a pretty good bit. when i press the gas it accelerates then drops in rpm's for a few seconds then shoots back up and accelerates like normal. its really annoying especially when im pullin a trailer with some weight and it does it..... any idea on why its doing this?