Help with power loss issues
 

I drive my truck for like 20 minutes and it runs fine but after its warmed up if I shut it off and turn it back on I have very sluggish acceleration. Feels like I'm pulling something heavy. I really have to put the pedal down to move. If I shut the truck off for an hour or two and then start it its back to normal. It only happens after its warmed up then I shut it off and start it again. Anyone have an idea what this could be. It's a 2007 Tahoe with 350 000 km