Engine shaking and white smoke coming from muffler , what could cause this ?

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Truck was running fine all day , went to the store and once I got back in it didn't want to start but once it did the engine was shaking and and making nosies white smoke came from muffler , after pressing on the gas for a little while the shaking slowed down and nosie stopped complety and was able to drive it home , started a hour later and the same thing happend again