Hi!
Hopefully, it was just something that has gone down the wrong way, both into the nose and into the airways and that will right itself over next few hours, likely when drinking too greedily. Keep in mind that guinea pig airways are very narrow and that they are not good mouth breathers, so even the smallest obstruction is always very audible and can sound rather alarming.
If you are worried about a URI (respiratory infection), please be aware that this is a bacterial infection and not viral human cold and that symptoms differ to those of a human cold. Typical for the onset of a UTI is raspy or crackly breathing from the throat or chest area and not sneezing or coughing, like in a human cold. Sneezing is much more likely a reaction to an irritant like hay dust or pollen or it comes as a nose clearing measure at the end of a 'piggy wash' (a few times a day) and coughing from greedy eating. Only if sneezing or coughing happen all the time and for hours on end should you see a vet.
Laboured breathing with heaving sides and possibly clicking from the chest (not the mouth) can indicate pneumonia in which case please see a vet as quickly as possible; just so that you are aware of what you need to look out for as these things are very often mixed up in online advice.
If in any doubt and if the breathing doesn't settle, then please see a vet. All I can do without access to your piggy and only relying on your description (weird breathing is a very wide and very subjective field after all) is guess but decidedly not diagnose. I hope that you can understand that.
