In answer to your first question: No. Men and boys sleep in anything from the nude to long-sleeved pajamas.
You're certainly not alone if you like to sleep in a tee. Don't ever let anybody (including yourself) make you ashamed because you aren't in the majority about some personal choice!
On the other hand, if you WANT to sleep shirt-free but can't, just keep practicing. For several nights in a row, you could leave it off, toss & turn for (say) half an hour, pull it on, then repeat the next night.
Eventually you'll either adjust and begin falling asleep the way you want to or decide it's not worth the attempt.