Check engine light comes on and the turns off when stop and restart it

Fires right up, step on gas, has nice power, but as I go, the power isn't there anymore and it stays kind of monotone throughout all the gears slowly. If I step on it it doesn't go faster it just slowly speeds up. And then after 45 MPH if I step down more I can hear clattering like an old truck does when it overheats. But it's not overheating.
if I cruise, it's fine, but when I try to get ahead of traffic I can hear it clicking like the lifters making noise (check engine light comes on). It's only after a certain speed it does this, but I can cruise all day everywhere. The power is just not there. And when I restart engine light is gone.