My betta fish keeps flaring at its own reflection and looks stressed out

I recently moved my betta fish into a new 2.5-gallon tank with a nice plant and a little cave for hiding. I made sure the water parameters were stable and the temperature steady at 78°F. However, I noticed it spends a lot of time near one side of the tank, constantly flaring its fins at what I realize is its own reflection on the glass. It looks pretty stressed, sometimes even rubbing its body on the glass.

I’ve tried dimming the lights and placing a background behind that side, but the behavior keeps coming back, especially when the room is dark and there’s a slight reflection. I want my little guy to feel calm and happy, not on edge all the time. Has anyone dealt with a betta that’s obsessed with its reflection? What worked for you to reduce the flaring and help your fish relax? Would changing the tank location or adding more plants help, or could this be a sign of something else going on?