i tranfered my oscar to new tank, now lethargic

this is the 2nd time in 1 1/2 years that i transfered my oscar to a bigger tank. usually he will lay on the bootom of the tank for a while all lethargic and then he will be fine. this time it has been several hours and he still is lethargic and not acting right. he turned white at first which i think is stress. his color has come back but he is not moving unless i try to encourage him, then he stresses again. so i left him alone and he  is just getting worse. any ideas what is wrong or what i can do? water temp is the same as old tank