My earliest memory is of a time when I couldn't speak. According to my parents, I'd started to speak around the age of 13 months, so this would've been when I was around, hmm, 6-20 months old?
I'm kinda sensitive to acceleration -- you know the feeling in your stomach when you're on a roller coaster ride? Sometimes I get it when people with very similar physical characteristics sitting right next to me don't.
Anyway, this memory involves my mother carrying me in a carriage down the stairs. I distinctly remember a) that feeling in my stomach, b) wishing for it to stop, but c) being unable to communicate this to d) this person carrying me, e) who I love(like?) and trust. I do not remember feeling any fear.
It's not that different from 'thinking with feelings/without words' as other people have pointed out. It's similar to not being able to express yourself due to shortage of words or brain power, or just squeezing the hell out of your significant other in bed in order to express what words cannot.
Note: I know a bit about memories and memory reconstruction, and I'm sure this is a genuine one. I've also thought and spoken about it from the very first time I've 'remembered' it, so hopefully none of the details were added later.