Should you tell people you are shy?
There are times when telling people you are shy could work in your favour. When I started my first university course, I felt very uncomfortable and my shyness took over. I soon realised that I was coming across as being unfriendly. This of course was the last thing I wanted, so I told two classmates that I was shy and that it took time for me to feel comfortable in situations like this. They informed a few others and everyone was very nice about it, a few others even admitting feeling the same. It was a risk, but one that paid off. (And I even found myself speaking up in tutorials, that was a big first back then).
But likewise there are situations where where telling people you are shy would put you at a disadvantage. This is espeically so in a business environment. The risk you take in telling someone you are shy is that it sets up their expectations of you. This can be a hard thing to overcome especially so in a professional environment when others can take advantage of that fact.
So it does depend on the situation and the people involvedl. It is also important to remember that taking steps to overcome your shyness is always better than telling people you are shy, and then using it as an excuse to not get involved.
