This is not the normal behaviour of MySQL. Have you searched in the log files what the reason is for this crash? I am thinking of the system either running out of file descriptors or running out of memory / swap space.
If you can't find the reason for crashing, the following script can help you in CRON:
#!/bin/sh
NUMBER=`ps --no-heading --user mysql ¦ wc -l`
[ $NUMBER -eq 0 ] && put here your restart command
It first looks for all processes running as user mysql. It counts the number of lines in the output of PS and stores this in a variable. If this is equal to zero, it executes the command behind the &&.
You should replace the '¦' with the proper one without the hole in the center, because the posting software on this forum changes the original character.
