True random can lead to strange surfaces. It seems you would like to have just a wavy surface. That's easy to do using trigonometric functions. Here's a parametric plot for you with simple cos for a start. You can play with the function, adding further trigonometric functions such as a sin expression to it, or using factors.
\documentclass[border=10pt]{standalone}
\usepackage{pgfplots}
\usepgfplotslibrary{colormaps}
\begin{document}
\begin{tikzpicture}
\begin{axis}[
view={120}{40},
grid=major,
xmin=-4,xmax=4,
ymin=-4,ymax=4,
zmin=-1,zmax=10,
enlargelimits=upper,
colormap/bone,
trig format plots=rad,
]
\addplot3 [ surf, domain=-4:4, domain y=-4:4,
samples=20, samples y=20,
variable=\u, variable y=\v,
point meta=u*v ]
( {u}, {v}, {cos(u) + cos(v)} );
\end{axis}
\end{tikzpicture}
\end{document}
