Firstly, this question is written by someone with very little knowledge of cars. So, please bear with me.
Some weeks ago, I was driving to work and smelled this horrible, thick, burning odour. Given that I hadn't smelled anything like this before when driving, I pulled over and opened the bonnet. (I don't really know why - I guess I was expecting to see fire.) But it looked OK. Nothing visibly wrong and I carried on to work; the burning smell died down after 2-3 minutes.
The smell must have happened again two or three times following this. I finally asked my friend in work who suggested it could be the clutch or a build up of something - he suggested some italian tuning. Since then, the thick smell went away.
However every so often I will smell this much lighter burning smell and unless I am totally mistaken, I think it's coming from the bonnet. Anyway, I took it to the garage today and they couldn't find anything at all. Clutch is fine and they couldn't spot anything wrong.
Can anybody offer some things to look out for or try so I can get to the bottom of this.