Could be the coil, although usual coil symptoms are either completely dead (no spark) or will be OK when cold, and then dead when warmed up.

Substituting known good coil is best way to troubleshoot. Replacement coil for 12XXXXX series Quantum engines is Briggs 692605 or 493237. Cost for OEM Briggs is about $35 to $40; Aftermarket is usually $20 to $25 on internet.

You'll have to pull the shrouds to check it anyway, so check to see if the coil worked loose. If loose, put a regular business card between the flywheel magnet and the coil, which is approximately the correct clearance and tighten the coil bolts. Be careful and keep in mind you're threading steel into aluminum - you don't need a 12" ratchet and a lot of strength.