Poor little Romeo
This is just my personal opinion - but it sounds to me, too, like a disc/back problem (I have one, and I know what I'M like first thing in the morning)...
Does he sleep soundly all night, and then have to kind of unwind himself?
I would make a very early morning appointment with my vet - wrap him up warm and snug in a blanket, and get someone to drive me there so I could hold him close in the car. If you can't video him, then he needs to be seen 'as is' - and he needs an x-ray.