Sporadic shuddering between 40-50 mph.

4 wheel drive crv. Sporadically between 40-50 mph the car will shudder like it is hitting the fog line groves. It will stop in 5-15 seconds. If I increase or decrease speed the noise/vibration will go away. It seems it does this on pretty flat areas. It also seems that the shifting is starting to get sloppy. This has been going on for over a year and is starting to get worse but it's never consistant.