Why do I tend to lose 3+ games in a row right after getting promoted?

I just got into Silver 4 and I immediately lost 3 games in a row. I took a break after each loss but it happens every time. It happened after getting promoted to B4, B3, B2, B1, and the initial S5. Is the game just trying to fuck you over? I don't understand, it happens way too much for it to be just a coincidence. Some games it's just a really good enemy team, some games I just have a bad time (but not enough to justify losing 3+ in a row EVERY TIME) and some games I get really awful teammates.

EDIT: Just lost a fourth game.