This has happened at least once to perhaps any woodworker. The thing is that router bits gather dust and resins, which causes them to get hot quite fast. If you overheat the bit and don’t clean it on time, the material may start burning. On the one hand, that’s quite inconvenient. On the other hand, you will be motivated to clean the bit regularly, which will save the carbide bit (if you are using one) from excessive heat impact and keep it sharper much longer. By the way, a dull tip will put the wood on fire much faster than a sharp one.