Yes it's normal for circuit breakers to get slightly warm when they have a high amp load going through them.
For example when my central air conditioner is running the circuit breaker will get warm but not really hot.
The central air conditioner draws a lot of amperage and electricity so the circuit breaker gets warm.
That would go for a circuit breaker that is powering a space heater as well.
The circuit breaker may get a bit warm but it should not be so hot that it burns your hand.
You should be able to comfortably hold your hand on the circuit breaker without burning your hand and if the circuit breaker is getting too hot then something is not right and it needs to be checked out.
The breaker could be just loose or have a bad connection or the breaker is not tripping when too much electricity is going through it.