Why is the speed of transaction on metamask so random sometimes?

Sometime my transactions go really fast and sometimes it's like they "get lost" and even though i pay very high gas fees it can take like 2 min for it to go through. They dont show up at etherscan etc. It just feels so random. Why is this? Those it have something to do with the RPC API infura that metamask uses? Can it help to get another one?

Would be helpful if someone could explain this.