hey guys when i start my car up it shoots white smoke out of the exhaust/tailpipe but then it goes away (only happens every now it then) stopped for a while and started again randomly. Was driving today and then a heap of smoke came out , pulled over turned car off for a minute of two checked bay everything seemed fine. started car again blew smoke then stopped (blew again while i drove down the road then stopped) pretty sure its stopped now. any ideas? i was thinking blown piston ring..

any help appreciated

thankss