2000 Mitsubishi Montero XLS 2 Wheel Drive - It Shudders!

My son has a 2000 Mits. Montero XLS 2 wheel drive. Under medium acceleration it begins to shudder! Pressing on the gas doesn’t get it, slowing down does. Then, under acceleration after that, it seems to go away. It’s beginning to happen more and more now. So, I was thinking it may be u-joints or transmission? I’m hoping one of Click and Clack’s great listeners might have a suggestion - other than get rid of it! LOL

Thanks - Mike V

Does it seem to do it more as the operating temp increases? Mine is doing something similar but I noticed if it’s cold (first thing in the am) it doesn’t do it near as much as it does once it reaches full operating temp.