Ok well, I was playing a game and I was lagging at the start so I had to leave. Then I reconnected and was still lagging. After resetting my computer, I wasn't lagging, so I just played the game like usual.. After I won it said I got suspended for a day for leaving games.. Was this glitched or something?

Hello snarkky. If I understand your post, as soon as that game ended, you were suspended. Assuming that is the case, you were suspended for leaving a game further in the past, and the timing on the ban was just a coincidence. It takes some time for the tribunal to go through all the reports, and so any time you are banned, it is for a past transgression.

This happens when you leave a game too often even if you recconect. Had the same thing happen to me, asked Riot, said it was for accumulated leaves.

That would be the LeaverBuster system, which is automatic and quick. If you were banned right after a game, it's because you've disconnected in previous games. Even if you are in the game when it ends, if you were gone or afk most of the match, it'll ban you. If you have consistent connection or computer problems, fix those before playing the game or you'll keep getting longer and longer bans. Other players will appreciate it too.