neurotic behaviors

I am very lucky to be able to spend most of my time at home. However, I do from time to time need to go in to the lab or run out to the store or just for whatever reason to leave the house for a bit. The parakeet entertains himself just fine, but the tiel does not. He doesn't play much, and when I am gone he literally stands in the corner on the bottom of his cage and just stares at the corner. He also will hold things in his beak and repeatedly touch them with his tongue. It breaks my frigging heart that he has these neurotic behaviors. If I am home, even if he is in the cage, he does not act like that. Any advice? It's seriously heartbreaking to see my buddy like this.

No he is not sick, it is only when I am gone.

Sent from phone

Consistency... however limited... I believe that's a key.
My story...
I was in college when I got the Rbird and then grad school, so I spent LOTS of time with him. Then it was time to go to work!
There were years (about 25 of them) when 5-6 days a week, I was gone at 7:30-ish and back at 6-ish.
Some did and will consider me wrong and think I should have re-homed him.
Anyway, here is what I think made it work.
I moved and got new jobs maybe 5 times or so. BUT...
Every morning, he had at least ten minutes, and every evening, he had 20 or so. I have always kept him on a natural light schedule, in a separate room, so sometimes those times together were in the dark. During the day, he had a big window looking out on something interesting, a television on one of his favorite channels (Music channels, CNN - he loves talking heads), a biggg cage, lots of fun foods, and a few toys that I changed out regularly).
He KNEW he could count on those two crumby sessions a day. Somehow we both made it.
I'm now retired and times are pretty good again. But when I first retired, he was standoffish and aggressive, at times, and not nearly as affectionate and cuddly as he was 30 years ago. Of course, he became a rooster at about 4-5.
He is famous (infamous?) for his quirks, weirdness, and overall trouble-maker-ness. I take responsibility. Today he is flighted, fearless, spoiled, and adored. We worked it out. I spend most of the day with his bad self now, and I know we are back in love. I guess my motto is... don't give up, do your best, and don't be unhappy with the results. Love your bird and yourself for what you are, separately and together.
Good luck to you.
I admire your love for your darling.

Oh that's too sweet and sad! Is there something special you can give him just while you're out? Like millet, something he loves and can look forward to that you reserve for only those times.