I have a 250cc buggy and I went out to the shed got in and I could hear the engine turn over but it wouldn't start the it did start and cut off about 5 seconds after starting could you please tell me the problem thanks

Dirty carb most likely... you store it with fuel in it, don't you? If the answer is yes... then its definitely the most likely issue. Old gas leaves varnish like deposits everywhere it contacts it, and nothing is more sensitve than jets.

Clean the air filter, fill with fresh gas, remove the spark plug, spray in starting fluid or gasoline, install a cleaned or new spark plug, and start the engine. It's best to use full synthetic engine oil, especially this time of the year. If the problem persists, you will likely have to clean the carburetor. Add fuel stabilizer to the gas and run the engine several minutes, if it won't be used regularly.