Anxietyboy, this is a common symtom of social anxiety. The tension causes facial muscles to freeze. If you're seeing a therapist or have a gp you might want to talk to them about this. It seems to happen mostly with males like other physical signs of nervousness such as excessive sweating or blushing. I've heard of guys who say thy get so tense that they can't even turn their necks. If I remember correctly beta blockers tend to offer some relief. Again talk to your doctor and ask what they recommend. I would imagine this is very distressful for you.
"Until one is committed, there is hesitancy,the chance to draw back, always ineffectiveness."