Guy texts me 24/7 and then suddenly stops?

I had a coworker who was pretty reserved but very cute to me. It took us a while to start texting due to us both being somewhat shy, but once we did, he really started opening up to me. He would tell me all about his day, share his weird insightful theories with me, and even tell me things about him that I'm sure only this close friends knew. We were really close and I felt so accomplished for gaining his trust and friendship.
He even texted me nonstop one night to where he didn't get any sleep for school the next day, mentioning that he would "rather talk to me than fall asleep":).
However, a day or 2 after that night, he suddenly stopped. He wouldn't reply to any of my texts and I eventually stopped because I didn't want to seem like the idiot who couldn't take a hint. :/ we even stopped talking to each other at work unless it was work related. This went on for months until he eventually quit for another job. Months after he quit, he came back to visit his old job and saw me there and talked to me like we were friends again. He even texted me about a week later, but every time he texts me, it only lasts maybe half a day and I'm always the last one to send a text. He's always nice and seems to want to talk when we text, but he never really keeps it going. Is he just really shy and maybe got scared from his feelings for me? Or was he just suddenly not interested?
He got scared from his growing feelings
Vote A
He changed his mind and wasn't interested
Vote B
Select age and gender to cast your vote:
+1 y
Also, he remembered by birthday after only telling him once and he wished me a merry Christmas :/
Guy texts me 24/7 and then suddenly stops?
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