Is it common? yes its very common and many people have experienced dissociative type memory problems for many reasons...depression stress, bipolar, grief,.....

for example

sometimes it happens due to my dissociative issues, sometimes it happens due to my bipolar disorder, sometimes this happens to me because I havent gotten enough sleep, sometimes it happens to me because I didnt eat correctly or at all, sometimes it happens to me due to my work stress, sometimes my medications make it happen.

what helps me is doing my breathing exercises/grounding exercises that my treatment providers have taught me. I do yoga/mindfulness activities also take breaks when dealing with stressful things and I make an even stronger effort to self care issues, and I contact my treatment providers so that they know whats happening and can help me get back on the right track again.

my suggestion...contact your treatment providers. they can help narrow down why you are having this type of memory problem and help you devise a way in which will help you to remain more focused/aware/mindful of your surroundings and make it so that it doesnt happen at all or so often.