Thanks for your reply.
I had actually done that (it is 1 month beyond warrenty). The tech at the store, did take it apart and look at the vibrating mechanism and stated it to be fine. When he put it back together, naturally it worked fine. Then the next time a call came in, it did not work. This has happened three times. I have 6 months to go on my plan so a new phone would cost several $$$$.
My feeling is that I am stuck with it unless I want to put out the $$$$ now.
I keep thnking that something may have become loose but who knows. Would a battery becoming bad do this?