I have just bought a new tv, Sharp LCD 37-XD1E. Using Sky (awaiting HD to be fitted). Have noticed today on several occasions, that the picture seems to briefly zoom in and back out again. Any ideas on what the cause of this could be? Its happening right now while I am watching Star Trek.

Your set must be on auto.

If its screening a non 16:9 picture it may automatically zoom when it senses dark areas at the top and bottom of your screen.

It thinks the image is a letterboxed image.

But auto is best as this will allow it to switch from 16:9 and then back to 4:3 when watching non widescreen programmes (unless you like 4:3 programmes stretched or distorted)