Why is it making a clicking noise when the turn signal is disengaged?

I have a 2000 S10 Blazer/170,000 miles. Was recently in the shop (about 3 weeks ago) for oil change and inspection, mechanic did not notice any new problems except that the fuel filter will need replaced sometime within the next year. However, last weekend when I was driving I noticed that whenever I used my turn signal and then put it back to center, the clicking noise continued intermittently while I was driving. It was not very loud, but definitely noticeable. And then today, as well as the intermittent clicking sound when the turn signal was not engaged, I also noticed a faint humming or vibrating sound, though the car does not seem to be driving any differently (no difficulty with steering, acceleration, braking, etc). Suggestions on what might be causing this?