Yeah that happens to me too, but mostly when I'm in social situations as a result of anxiety. Atomicc points out that it occurs with BPD but it is also associated with many other mental conditions. Extreme anxiety or past trauma can be a cause (remember "trauma" is relative) but maybe other things too.

I don't think it necessarily feels like being on drugs, but some drugs can cause dissociative feelings. It's not nearly as entertaining as drugs though. Cocaine actually used to make me more dissociative I think but that's because I'm already an anxious wreck. Don't do drugs.

Read about dissociation on wikipedia. Good luck.