I think Toshiba notebooks are notorious for this.(?)
Can you go into the boot menu by holding in "F2" (I think F2 anyway) when booting and see if there is an option in there for enabling/disabling the system beep. Maybe yours is the same?
If not that, then could be:
1. A damaged/faulty motherboard could be the culprit. If you have a warranty they should fix it for free. (If it is the motherboard).
2. Overheating?
If you could give specs on the laptop. eg, Make, model, age etc...?
But if it's beeping while otherwise operating normally (which is how I read the original post) then it's surely unlikely or impossible that these are BIOS beeps?
Unless it was overheating and is now cooled down.No harm to check the beep codes.Make sure the air intake for the cooling fan(usually underneath) is clear,especially if you are in bed while surfing.