I have a 2006 f250 and the doors lock all by themselves I don't even have the key fob near it l shut the door and it locks if I use the key fob to unlock the horn beeps anyone got any ideas?

I have a Tacoma that does something like that. I can use the fob to unlock the door, and it will relock about 20 seconds later if I don't get into the vehicle during that time.

Does it have an aftermarket alarm/keyless entry etc. or is it factory?

If its aftermarket I would assume that is your issue and something is amis.

Do you have any check engine lights on? Does your truck have the feature where when you go over 15 or so mph it locks the doors automatically?

Keyless entry is factory and they lock at certain speed

Reprogram your Fob . Look it up in YouTube . Just turn your ignition to on and off 8 times fast as you can but on the 8th time leave it on . You'll hear the door locks open and lock . Then on your Fob just push the lock button then the open button . After this turn off ignition and test the Fob . This should fix the problem .If it don't then take a pocket knife and pop open the Fob and change the battery and follow that procedure again . Most Fobs take a CR2032 battery . Good luck . Dealers will charge a couple hundred for that job . If you have 2 Fobs you must do this button pushing on both Fobs before you turn the ignition off , other wise only the Fob you programed will work and the extra one will not .

is one of the door lock actuators not working or sporadic/kinda working funny?

Try this..
https://www.fordf150.net/howto/autolocks.php