Dennis Prager, the popular radio talk-show host who is also a devout Jew, was once asked about this on the radio. He said it was merely a cultural phenomena, and that praying Jews have just customarily done so. He never questioned it as a child and, when he grew older and encountered Christians who remained relatively motionless in prayer, he was surprised!
To me, it seems a good way to stay focused and engaged in prayer. During the Mass, for example, there are many traditional movements that keep one involved: [LIST]
*]Signing your self with holy water when entering and at appropriate times during the Mass.
*]Genuflecting before the tabernacle before entering the pew.
*]Standing and kneeling at the appropriate times.
*]Folding one’s hands when waiting to and recieving Holy Communion and during moments of intercessory and liturgical prayer.
*]Bowing when passing before the altar.
*]Slightly bowing the head at the name of Jesus.
*]Making a small cross at the forehead, lips and over the heart before the reading of the gospel.
*]Striking one’s chest during the Confietor
*]Bowing during the Creed at the line “…was concieved by the Holy Spirit and became man.”