Need a key holder
 

At first I just put the key in my pocket. Too often the SB open button would get hit the SB would open at the silliest time. I put the key in a holder from my wife’s Lexus and that reduced the issue. Today not only the SB opened but the alarm sounded.

Is is there a hard key holder to keep this from happening?

Yes, the hatch. But Audi doesn't call it a hatchback, it is a sportsback. Like BMW makes a sports activity vehicle, not a sports utility vehicle.
It is the key. The fool thing is curved with the SB open and alarm buttons most exposed.
Think I'll start putting it in my backpack.

I keep mine in my front pocket and have never had this problem. If it's really a recurrent problem then maybe you can put it in the center console or if you have the key by itself just put it in the little slot next to the gear shifter.

You can code a longer delay via OBD11/VCD. I haven't done it yet, but I have been meaning to because the A5 seems way more sensitive than my MY14 Q5 fob. I took a screenshot of the coding, but it's on one of the threads in this forum.

I think your pants are too tight.

I got these for my A5. The FOB slips into the case. The case requires a bit more pressure on the buttons to activate. No problem with accidental opening so far
https://www.ebay.com/itm/3-Buttons-S...item56a65b3bbc

I got the dark blue and black.

:D