It is hard to diagnosis without seeing the unit, but this sounds like a fuel problem. Did it run ok when you picked up from the dealer?
If you have filled the tanks with gas that you have had for several months you may want to drain that out and put in fresh gas before you take it into the dealer.
Todays fuel will not last nearly as long as fuels of just a few years ago. Most manufacturers are oxygenating the fuel to help it burn cleaner but it also causes the fuel to breakdown much faster. Storing fuel over the winter will require a fuel stablizer to keep it from spoiling.
There may be other reasons for your problems that the dealer should be able to resolve.
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