(Let's say it's a little AU were allspark got on earth in 21 century (; )

Allspark is far away from Cybertron and now Optimus needs to finds it. Energon is low. Autobots are too tired to even stand now. So now he needs to do everything by himself.

Allspark was detected on organic planet... Earth ,as things on this planet call it. Humans such fragile creatures, not only physically but mentally too. He quickly understood it he doesn't need any human seeing him so he found himself another alt form. Human truck is thing he's most comfortable with.

There he is driving through forest at the same time reading about humans.

After few hours he finally found where allspark is. He transformed and squeezed through trees , making sure he doesn't break anything or anyone

Finally he sees allspark but ...Oh no. A human- you. Right Infront of him , reaching out to it.

What he can do now? Confront a human? Could be too risky , human can have heart attack or something from seeing literal alien Infront of them, plus he's larger than you.