Constant crashing problem

I have a constant (but not daily) crashing problem that always happens right before champion select. This problem first occurred to me around October. The problem typically happens whenever I just turned on my PC or I kept my PC on for a long time. Sometimes I'd have to wait 5 min later than my teammates, which would result in a remake since I didn't fully load and the game already started. Sometimes it would load to as long as 15 min just to get into the game, even if it already started 10-15 min earlier. Eventually, I'd get leaverbuster at the end of the game in most situations for as long as 20 min due to this recurring problem. I was wondering if anyone had the same problem as me and if there's a fix to it, since I neither want leaverbuster for such an guiltless problem (technical problem) nor will I want to load for long periods of time. Any solutions?