Arduino Mega taking random inputs+Bluetooth+Multi Serial

Hi People,
I'm working on a robotic project using Arduino Mega as a controller which is connected with Robot's on board Windows 8 computer via USB Cable... Now Serial Port 0( Arduino USB to computer) is used and the Serial port 1 is connected with BTBee Bluetooth Module(| 502: Bad gateway ) is Based on the popular HC-05 Bluetooth Chip.... The Problem is when the robot is On,State of Computer is whether On or Off and also Bluetooth module is not connected with any Computer,robot gets some commands and moves. i.e- Nobody given commands to robot but it starts moving :astonished:
But.the strange is when robot starts going crazy, it follows one command at a time... Say it goes Right for 50 Sec and backwards 30 Sec... Some times.. Relays which i used in the Robot Goes ON.. Sometimes the Servos...
The Robot Program is like 1 for Forward,2 for Right and 3 for Left etc... 'A' for first Relay ,etc.... 'a' for first Servo

So,what can be issue
1.Is it a Bluetooth Serial Data Buffer
2.Connection Issue ?
3. Any other things...

its happening from past some 1 week only... Previously this problem was not here...