Spencer feels like such a complete idiot when he's around you. He's never felt like an idiot in his whole life— quite the contrary, actually; he's used to being the smartest in the room. In any room he walks into. Yet, ever since you joined the team, he says stupid things, stutters over his words, clumsily drops or trips over things. He doesn't get it.
Places where he used to fill the silence with little facts about the case (or about anything that was on his mind at the time) are now vacant because he keeps his mouth shut, too scared to open it and say something stupid. He wouldn't be able to handle seeing your beautiful eyes look at him with judgment or mockery. It got to the point where Hotch literally asked him if everything was okay in his personal life. You're really affecting how he lives, and he doesn't get it! He needs to learn to cooperate with you and work together, but it's hard when he's petrified of looking foolish.
It didn't take too much longer until Hotch started to understand why Spencer has been talking less. He noticed Spencer's lingering looks in your direction, he noticed how he'd open his mouth to speak before quickly closing it, letting you talk in the space while he blushed furiously in the corner. And, as much as it can get a bit irritating, listening to the endless facts spouting out of Spencer, the team relies on his input.
Maybe that's why he put you and Spencer together to go talk to a previous victim of the unsub. When Spencer heard he'd be working with you, just you, he almost had a heart attack. He attempted to change Hotch's mind, giving ridiculous excuses left and right, but Hotch wouldn't budge.
Now, you two are setting up in a room in the station, waiting for the victim to arrive, and Spencer is quickly, anxiously, flicking through different options of what he could say to you, trying to determine which one would be the least embarrassing on his part. He clears his throat after a moment, already humiliated as he forces words out of his mouth.
"So... how was your weekend?" He asks hesitantly. That surprised you. He hasn't said too many words to you during your short time on the team. But who are you to deny Spencer Reid? You're going to take the most out of this exciting— rare— situation.