So I'm fairly comfortable around a bike but this is an issue I haven't encountered before. I have a new bike (Jamis Renegade Expat). The bike has a compact double chainring.

On the last 2 rides I have had the following issue. It doesn't happen every. I will shift to the small chainring without issue. When I then attempt to shift back into the large chainring, it lever moves as if it isn't even connected to the cable. It has no resistance and the front shifter doesn't move.

Today after about 15 miles I randomly tried the lever and it shifted into the large ring without issue.

Like I said I have had this numerous times, although not every time I shift down and back. And it does seem to work again eventually.

Since the bike is new I am planning on taking it back to the dealer, but before I did I was figuring I would ask in case it is maybe something silly I can just fix and not waste the time taking it back for repair.