Is it okay to "refuse" to be a pallbearer at a funeral?
 

I'm afraid I will be asked by my family to be one of the pallbearers at my grandmothers funeral and if I'm asked (extremely likely) then I really, really do not want to do it. I have horrible social anxiety which is even worse with family gatherings and the thought of having any sort of attention on me at the funeral and people looking at me or me having the potential to make a mistake or look awkward makes me feel sick. I feel if I had to refuse this invitation I would look really rude and selfish and "difficult" but I honest to God just can't do it. I'm terrified of being asked.

I just want to be in the background as much as possible but how on earth do I say this without sounding disrespectful?

I think it's perfectly valid to decline the question of doing it. Could you explain your reasons to your family? Or even just one family member? At the end of the day, the day will be hard enough on you without adding pressure. However, it's worth remembering that the focus will be on your Grandmother and her life not you.