Not gonna shit up the voting thread with this reply so Imma summon y'all to my salty thread for it but:
I had one flashback, one time, when I was like 16 or so. I was laying on my bed going to sleep one night when I got a body buzz and started hearing a ringing. I was like "WTF this feels like I'm on acid"
Then for like 5 minutes I hallucinated the earth as a wire frame mesh that tilted and rolled in various directions about 5 feet in front of my face.
Then the body buzz went away, the hallucination faded and I was like "Well that must have been a flashback because I dunno what else that could be" and I'm pretty sure that's exactly what it was.
It did feel for 5 minutes like I was just peaking on acid again. Not uncomfortably in any way.