Just to add another possibility to consider.
One of my boys went thru something similar: was opening and closing his mouth, twisting his head around, licking his lips and generally moving is tongue around inside his mouth. I tried flushing his mouth, examining it for something being stuck in his teeth and couldn't find anything. Called the vet, who also suspected something was stuck so came out. After examining him thoroughly, it turned out he was having some gas issues and as soon as he passed that, he was fine. It happened a few more time, on and off over a couple of months, then stopped completely. Never did figure out exactly what was causing the problem, so I'm assuming there was something about some of the hay that wasn't agreeing with him 100% as he lived on a dry lot.
Lavinia, George Too, Calvin (PPID) and Dinky (PPID/IR)
Nappi, George and Dante Over the Bridge
Jan 05, RI