  We present an extensive study of the vortex dynamics in
Li$_{0.8}$Fe$_{0.2}$OHFeSe single crystal, which is prepared by intercalating
insulating spacer layer Li$_{0.8}$Fe$_{0.2}$OH into FeSe. Absence of fishtail
effect and the crossover from elastic to plastic creep are observed similar to
the parent compound FeSe. However, when we apply collective creep theory to the
magnetic relaxation data, the obtained creep exponent $\mu$ is found to be
$\sim$ 4.1 much larger than the predicted maximum value. Besides, the elastic
creep in the vortex phase diagram of Li$_{0.8}$Fe$_{0.2}$OHFeSe is found to
reside only in an extremely small region. Such a large value of $\mu$ and the
small elastic creep region may be originated from the weakening of coupling
between the vortices in neighbouring layers by elongating the layer distance.
It may indicate that the vortex structure of Li$_{0.8}$Fe$_{0.2}$OHFeSe is in
the crossover regime between elastic Abrikosov vortices to stacks of pancake
vortices. Our study also suggests that the intercalated FeSe is a promising
candidate for searching intrinsic Josephson phenomena.
