Almost every time I start the vehicle the first time of the day. It will only do about 20mph no matter how long i let it warm up or even taking it around the block. However, if I turn the engine off and restart it the transmission will let me go between 30-40 then slowly increase the further I travel. What is causing it to start off in limp mode every morning or if I haven't driven it within the last 2 hours?

95 Montero 3.0 24v Newly Rebuilt; Automatic- work in progress