How to get rid of code P0300

My check engine light just came on and it's throwing P0300 which indicates random multiple cylinder misfire. It drives ok still, with occasional rpm fluctuations at idle. I haven't changed plugs at all, could that be the issue? Also, I've been using regular 87 octane gas for awhile due to the gas prices. Overland manual calls for 91 octane and up, could that also be the cause of the misfire? Is it ok to keep driving the vehicle? Any input would be greatly appreciated. Thanks

Rob