Engine hesitation?

[Chevy409]

This is probably a no brainer but just recently, my engine started hesitating when i slowly step on the gas, gives the feeling like the brakes are on but they aren't. the truck's been off the road for about the past week because i was fixing some body and put in a lift but nothing with the engine was changed. The weather has dropped significantly though, could it be the coldness? The problem does fade as engine warms up but it's anoyying when I first get going. Replace the thermostat with a 195 (160 is in there now)? Something else? Any tips would be appreciated. thanks