Possible flat spotting of tires. Did you increase tire pressure during storage? During storage the tires should be increased to the maximum placarded cold pressure or 40 psi, whichever is greater.
You should have the tires analysed by a Hunter 9700.
Go to www.gsp9700.com
and you should be able to find one in your area. If the tires still have more than half tread depth, you might be able to get an adjustment from the manufacturer on a new set.