727 wierdness

First make sure the fluid is full.

Then if that's not it.

It's probably either a case of a valve hanging up in the valve body, governor or an internal fluid leak.
I'm leaning towards a fluid leak because usually if internal damage is causing valves to hang up it will be on the first drive after sitting over night.
OR, it could be the governor valve or a valve body valve hanging.

JMO