Hi Mbuthia,
Check your Memory utilization - both RAM and Swap at the particular times you experience the drag in your network and nail down the service over-utilizing the Linux box' resources.
You may also consider checking the processor utilization. This is quite common when a particular application in your system hogs most of the system's memory.The
"top" command comes handy in this but there are plenty of
other options to carry the checks depending on your desired output and
also preference.
Crons... well they will assist in automating the restarts but you won't have sorted the cause of the problem.
Regards,
Chris_w.
dabnix@gmail.com