2003 Mitsubishi Outlander

I have an Outlander and recently a shudder in the engine (by my guestimations that is where it comes from) has started to occur between 35-45 Mph. It drives fine at high speeds and most of my driving is on the interstate at around 70 Mph. If I accelerate to 50+ Mph there is no shudder during acceleration. If I drive between 35-45 Mph, there is shuddering, I usually slow down and then accelerate again to get rid of the shuddering. It is a 4 cylinder, automatic,front wheel drive Outlander. Any idea on the cause of this engine shudder?