I used to have similar things happen to me when I was having manic episodes, or coming down from mania. I remember one time specifically that I left my house and ended up at the beach but I had no recollection of how I got there once I was sitting on the sand. It was a very strange feeling. After telling my counselor, she suggested I see the psychiatrist at the office and get an eval for medication because it was definitely a symptom of hypomania.

I haven't had this happen in a long time but I know that it can be semi worrying if you're not remembering blocks of time.