Raw data from Explicit Dynamics solutions are known to be full of noise and smooth results can be obtained by low pass filtering, but only by filtering every cycle in the simulation. You have to do this to avoid aliasing the signal. The data you are showing in the graphs might be one in 100,000 cycles. Look at the total number of cycles and divide by the number of points in the plot. You would need to very carefully setup the model to write out data from the one node of interest on every cycle because if you write out results for every node in the model on every cycle, you will run out of disk space. Read the following discussion and follow the links in that discussion to the paper that explains this in detail.
Regards Peter