I am on a VPS. The VPS has about 25 sites on it. This VPS

I am on a VPS. The VPS has about 25 sites on it. This VPS also hosts the multisite install; http://blogstarta.com.

There are sudden bursts of loads generated by blogstarta.com that hangs the database, and this puts the whole VPS offline for 3 to 10 minutes at a time. This now happens at least once a day.

What seems to be the problem? Server configuration problem? Some bad plugin?

The multisite blogstarta.com itself has very few sites.

Please help.