The problem is likely that one or more of your employers did not send their copies of your W-2s to the IRS in a timely fashion.
The IRS is going to need some time to figure out what you were actually paid and what tax was actually withheld (because if the IRS didn't get a W-2 then they also probably did not get the tax withholding that went with it). The IRS does not want to refund you money that wasn't withheld.
Watch your mail box and respond promptly to any letters they send requesting more information.