Problems after start up
 

96 XJ 4.0 auto and I'm having problems right after start up. I've researched the threads a bit and I can't seem to find anyone with the same problem. Vehicle runs great with just over 100K on it except after start up and I put in drive. It will start to accelerate normally then all of a sudden no matter how much throttle I give it, it kind of bogs down like its going to die until I hear and feel a kind of hollow "pop" under the drivers side where my feet are and then it accelerates fine and I don't have the problem again until I turn it off and restart it. Also taking my foot off the throttle and then giving it gas again when this happens makes it go away as well. It's not a huge problem more of nuisance but I want to make sure it wont lead to something serious down the road. I can't think of anything it could be and the vehicle has had this problem since I bought it. Any ideas?