Since I don't have any background information, it's difficult to say the full story. But it might be that in a new place or among new people, there is a Martin who has some sort of connection to the situation and you keep getting wrongly associated with him.
The fact that you say you're not Martin implies that there is some sort of misidentification going on. Maybe Martin is a colleague at work and your new coworkers keep getting your names wrong. Or it could be in a social setting, like a club or a group activity, where there's a Martin who is more well - known and people assume you're him without really looking closely at who you are.