Do I have the start of a receding hairline? (Photo)

It is difficult to make a diagnosis based on photos alone however there does seem to be some very mild thinning along the left hairline and temple.I agree that I would be hesitant to render any therapy at present-you can continue to document any potential changes with interval photos (every 6-12 months).If a change is noted at some point than I would recommend another evaluation with an experienced Hair Restoration surgeon.

While I agree it is difficult to see from your pictures for sure, I also agree it does look like what could be the start of male pattern baldness.
I recommend seeing a hair loss specialist who can perform a digitial microscopy and DNA analysis.  They will be able to tell you conclusively whether you are experiencing the onset of male pattern baldness.  They will also be able to help you with a treatment plan which will prevent any further hair loss and protect and keep a full head of hair for you.
You are much, much better off keeping all the hair that you have than waiting until its too late and your are struggling with rapid progression of thinning hair that only gets worse over time.  
Now that your hair loss has started you are permanently losing 10 hairs a day for every day you do nothing.  Thats 300 hairs a month you do nothing.

You are correct that time will tell, however it does appear there are changes, more widespead in the temple area, that would suggest early AGA (receding hairline) is indeed present. I would encourage you to continue to take photos every 6 months if there remains doubt.