Delayed Engagement in Drive

I have a '98 F150 4x4 with a 5.4 V8. When it sits for a couple hours and you try to put it into Drive, it takes forever to engage.

Once it gets going, it runs great and shifts fine into and out of all gears. Converter locks up just fine----overdrive works fine. And I never have a delay engaging reverse.

This thing has over 200K on it and I do not know maintenance history, so it could be just about anything. But do you think it could be dirty fluid or a partially clogged filter? Or how about my pressure valve??

Any advice or ideas would be appreciated?

PS. According to the sticker on my door, the tranny is an "E" Code 4R100A

change the fluid and the filter c if that helps if not then ur shift selinoid could be bad or out of adjustment