How can I train my horse to stop bucking?

He's only 5 and hardly has been ridden all winter because up here in MN there was ice EVERYWHERE until yesterday, when it started melting. I'm sure he's just feelin frisky from a long winter off, but how can I correct his bucking and rearing before it gets out of hand? He's really spooky; if I even lift my hand to scratch my nose while I'm on him he bolts. Thanks so much for any advice!