Worth removing the distributor cap and cleaning all the 8 contacts and rotor arm - check tension on the carbon brush for resilience. Good visual on the cap will tell you if it has been tracking under load.
Otherwise, leads and all the other faston's associated with ignition underbonnet, could even be the ignition coil breaking down.
If in doubt swap them out one by one these items are cheap compared to a moments hesitancy at the "wrong" moment.
