1. no-one on this website is clinically trained in MH - think psychiarists and or postdoc psychologists.
2. Dr. Goolge will give you lots of fearful things about symptoms
What you describe as 'dissocation' is quite a different beast clinically, and requires professional evaluation.
Actually I went through the vague symptoms you mention when I was a hormonal teenager. Just wigging out, and not aware of what was going on around me. Lasted a few years alcohol and weed didn't help.
If its happening regularly or more often, then maybe its just growing pains mixed with party drugs...but if it interferes with life, then seek professional help.
You also dont mention alcolhol or drug intake that can cause similar symptoms of disconnectedness or dissociation.
In response to your question, what should I do? - go see a GP
Is it bad? - no-one on this forum is qualified to answer! Could be a bit of teen angst, maybe alcohol/drug induced, nor forgetting PSTD...a long list. Best let a pro sort it out if your concerned.
Bottom line - if it gets worse and affects your quality of life, go see a GP.