I've been thinking a whole bunch about yandere Bayverse Optimus Prime, especially in the beginning of Dark of the Moon. This can be platonic or romantic 😌
You get hired by Sector 7 for some reason or other and have the incredible experience of meeting the leader of the Autobots on your first day. He finds you absolutely fascinating. You train under Ratchet to learn about first aid and instead of letting one of the other bots be your training dummy, Optimus himself volunteers to let you practice on him. You carefully work on the practice equipment, not letting even a drop of solder get on his paint job. He ends up being so relaxed while you work that his engine purrs so loudly that you have to shout to Ratchet in order to ask him questions. You end up dropping a wrench on him after getting quite literally rattled around from the purring, not that it causes him any harm, and end up apologizing profusely, much to Optimus' amusement.
"I assure you, little one, I am very capable of handling something that has not even scratched my finish. It's okay." He rumbles warmly.
He ends up seeking you out more often and eventually begins requesting that you be the human to assist him. You don't mind at all, clearly enjoying the stories about Cybertron that he tells you while you work on whatever it is that you're assigned. He seems to have a certain fondness for holding you and once you tell him that you like it, you barely have to walk anywhere on your own. He's always nearby during your shifts and you've stopped having to drive to work and back once he starts driving you. You never ask how he knows where you live.
After a few weeks, your relationship with Optimus devolves into him treating you more like a stress toy than anything else. When he's in a bad mood, he simply scoops you up and transforms into his vehicle mode for another round of giving everyone the silent treatment. You've learned to nap while he keeps you firmly buckled into his driver's seat. He holds you during meetings, either having you sit in one of his servos or on one of his shoulders. Ironhide teases you a bit for getting such special treatment, though it's never too bad. Optimus' bad moods have gotten significantly more mild and he is much less strict than he was prior to being around you. Secretly, there isn't a soldier on base, Cybertronian or human, that isn't grateful to you.
You don't understand Cybertronian customs, let alone nonverbal communication, so you always brush it off when his headlights brighten when you're in his cab. You don't ask why when he sniffs you when he first sees you or why he begins putting your favorite car air fresheners in his cab. You never realize that his engine is never so loud around anyone else. You brush it off when he ignores other humans in favor of asking if you've eaten and taking you to a drive-through during your lunch break or when he rushes you to Ratchet when you get a bruise or blister. You simply assume that he's being a good leader and that he values your skills. Optimus doesn't mind. He doesn't correct you. To him, it means that you're okay with him keeping you close and caring for you.
