Furry Friday: Strange Behavior

Any other day this little guy is the light of my life.  Wednesday evening he was anything but.  We were getting ready for bed, doing our usual routine.  I lift him up to the bed, proceed to plug in our cell phones, turn on his nightlight, and on my way back out of the room to take out my contacts I usually stop to give him a few snuggles before giving him his bed bone.  Unlike any other day though, it's at this point that he snaps.  Growling and snarling, he bites at my hair.  Scary!  Justin grabs him worrying that he was going to bite my face and in the process Justin's thumb gets bitten.  

Those who know Riley know that he's a highly affectionate little snuggle bug with Justin and I and our close family/friends.  With outsiders he takes a little to warm up and will sometimes growl/snarl if an outsider attempts to enter our house and hug Justin or I hello.  This is why last night was highly disturbing.  He's never lashed out like this at either of us.  My biggest concern is that something is going on with him that I am unaware of (seizures, back/neck pain, etc).  He'll be five this year, has been kept up to date on all his shots, and has always been given a clean bill of health from the vet's office aside from the chiding to give him less snacks. 

I have noticed, however, in the past few years though that lunar cycles seem to affect him.  He gets a little mopey around a full or new moon and will sometimes hide under the bed and chatter his teeth.  It's during this time that he'll usually come to me with his tail tucked and want to be snuggled and soothed.  Once the new moon or full moon passes, he's back to his chipper old self.  It just so happens that Thursday was set to be the new moon and it was on Wednesday evening that he flipped out.  I'm hoping these two things are correlated, but even still this sort of behavior is unacceptable and I'm curious if his being affected by the lunar cycle will soon require some form of medication.

Does anyone else have this issue with a pet?  What are the solutions you've found helpful?  I'd really like my little snuggle bug to be back to normal.