Help with unknown problem

[Will1985]

My thoughts are along the same lines as Smoothhound...does it happen when you are off the saddle?

 

[jig-sore]

chain ring bolts ??... oh the list goes on and on

 

[purplepolly]

oh the list goes on and on

We've helpfully narrowed it down to almost anything

 

[Randochap]

We've helpfully narrowed it down to almost anything

Termites.

 

[G-manUK]

Maybe it's my knees!
A lot to think about there. Thanks everyone. A trip to my LBS methinks, and let them puzzle it out!