My deja vu episodes were caused by epilepsy. I didn't know what it was for years. It seemed to be sort of a dream sequence that made me feel like I had been in that place or situation before, and then in a few seconds, it was over.
Then one day, I had a classic Grand Mall Seizure. Luckily I was not driving at the time!! These things are not to be taken lightly!! See a physician that specializes in seizures and have some tests. They will include some brain scans, etc. You will have a good idea then if you have some problem. You need to know if this is a real problem, BEFORE SOMETHING REALLY BAD HAPPENS. I have been on medication for years, and have been seizure free for about 5 years. It's not the horrible problem that it was thought to be in the past.
Have it checked out, you will be glad you did.