No—higher resolution does not make handheld shooting physically harder or inherently create more camera shake. What it does do is make it easier to see small amounts of blur when you inspect the image at 100% or try to extract every bit of detail the sensor can record.

In this case, the difference is also small because the D800’s pixel density is only slightly higher than the D7000’s. So at the pixel level, the D800 may be marginally less forgiving, but mainly if you’re “pixel peeping.”

For normal viewing or the same final print/display size, there’s essentially no meaningful difference in blur caused by sensor resolution alone.

One practical wrinkle: because the D800 is full frame, you may use a longer focal length to get the same framing you had on the D7000, and longer focal lengths can show camera movement more clearly. That’s due to focal length and viewing magnification, not because megapixels themselves make handholding harder.