H2O temp gauge fluctuation

[Ken Keith]

I noticed when my '88 5kcstq is warming up from cold, it seems 
like the water temp gauge rises to 1/4, and then falls down to the 
bottom, only to rise once again to 1/4.  After that cycle, it tends to 
stay normal.

I don't think it's my imagination, and I haven't checked it closely 
after I noticed it.  But I seem to remember noticing it once before.

Is this some kind of known symptom?

Thanks,

Ken