Mites / fleas??? Clean out with the ear cleaning "kit"
Is there a funky, yeasty smell? Take a sniff, if so, most likely a yeast infection. Trip to the vet for drops.
Try an over the counter ear wash from your vet or a pet store. Franklin used to have this issue and I'd rinse his ears and he'd be fine for a few weeks then he'd start shaking his head again periodically. The ear wash worked every time. She may also have something in there (like grass or a fox tail) and the ear wash will help flush it out if its not lodged in there.
instead of using q-tips I would use guaze pads, safer for cleaning the whole ear. our vet showed us how to thread the guaze pad into the ear and then pull it out, so then its clean.
The ear can also be dirty far inside where you can't see it. I have earwash from the vet for this. It could also be yeast.
So I went ear diving..and I'm probably the cause for the ear shaking..
when she first started to show signs of shaking, I cut her ear hairs. While diving, I found a big piece of hair caked in wax (attached.) I did find a small amount of black in her ear (as shown behind the flap), and I had a difficult time getting it out. I will still try the ear wash to make sure everything is out.