There is usually a
dd process running to copy data output by the kernel from virtual file
/var/run/syslog/kmsg, presumably so it can be kept (anything in
/proc is temporary state). Under normal circumstances this process runs from boot until you shut the machine down.
If you run
ps ax | grep \ dd you will see the process listed with its full command line. This command should not be consuming much resource at all so should be fine to be ignored.
Does the process show as consuming much CPU time in
top? What other processes are consuming CPU time?
It would be a good idea, next time the issue occurs, to run
top -n 1 and add the output of that to your question so we can see what it being reported.