Is carbonation in fermenter normal?

I brewed a belgian wheat that has been in fermenter for almost 4 weeks now and when i opened the lid to take a gravity reading, I got a little hiss as though i were opening a beer bottle. I took a sample into a cylinder to take a reading and took a sip. Not bad but i felt a little fizzle on my tongue. So I held my hand over the top of the cylinder and shook it. when i took my hand off, I got a big hiss and about 3 inches of head inside the cylinder. Is this normal? I thought maybe my airlock was clogged. nope. This didn't happen for my first batch so I wasn't sure if this was normal or if there might be something wrong. OG was 1.045. current reading is 1.008. Had bubbles in airlock for the first six days. It has been silent since then.

Nothing to fret about. Still liquids will super-saturate with gas during fermentation, and any amount of agitation will cause the excess gas to come out of solution.

Gotcha. Thanks for the quick response.