Hi, my name is XXXXX XXXXX I will be helping you today.
There are many things that can cause the door to open by itself. Unfortunately, it is a long list. It will take some patience and some thorough investigating to find the answer. Perform the following possibilities in the order that I placed them until you find the solution:
I would start by erasing all codes and then reprogramming the remote(s). See if that stops the "self-opening".
It could very likely be a short in the wiring especially between the wall button and the opener. I would try rewiring this section to see if that fixes the problem.
A defective wall button could be shorting the switch, causing the door to operate on it's own. You would need to replace the wall button to fix the problem.
A defective remote could be shorting and causing the door to operate on it's own. To test this you can remove batteries from all remotes and keyless pads to see if the self opening stops. Do not forget about spare remotes stored in drawers, etc. Using the lock feature (if you have this feature) on the wall button will disable the remotes, so this is another way to test if the remotes are the cause.
Other possible causes but not nearly as often as the ones above, are a defective logic board inside the opener, nearby signals from police/ fire stations, cell phone/ radio towers, etc. I have even heard of a newly installed Verizon Fios cable tv box that was interfering with the codes of the opener and the cable box had to be replaced.
You are going to have to find the problem by "process of elimination."
Also for protection, unplug the opener to prevent it from opening at night and when you are away, until you solve the problem.
If you need further help or clarification on this answer, please do not hesitate to reply to this post.