Most likely what it is. Pretty annoying. Before taking it to the shop, try lowering the top and then putting it back up to make sure its seated correctly. While it's down, wipe clean the window frame gasket against which the top seats to make sure there's no debris. Put a tiny bit of WD40 on the top lock mechanism and the catch that it grabs onto (just be careful and don't spray any on the fabric top).

Don't do it unless the outside temperate is at least 50 degrees though. Cold makes the top brittle and you can damage it.