Mine does that to, esp when its below 40 deg. The 4ways come on right away but blinker is slow. Its fine in warm weather.

That means that the grease in the switch has hardened and is keeping the points in the switch from making. I don't know if you can fix this by spraying. On mine, I had to take the switch apart and clean all the old grease out, (it had the consistency of wax). Once cleaned and regreased, it worked like new.
-RP