For the last few hours I've noticed that some mysql processes have been running for 10+ mins and keep spiking to 60-100% cpu usage every few seconds.

Normally (for the last few months of monitoring the server) mysql processes normall use less than 1% cpu and only rarely spiked to 15%.

All of a sudden every 3-4 sec one or 2 mysql processes are spiking up to 100% cpu usage .. any ideas what could be going on?

check if there is a problem with some scripts that use mysql database..... check out if mysql partition is not full either..

mysqladmin status
mysqladmin processlist