Texas Heat and Coils

[btmed]

60 plus days of 102 to 107 degree heat here in texas. replaced coils and plugs just last summer, meyles, for my 2001 x5 3.0 120,000. was running rough this week and decided to let moritz diagnose. They found 1 coil bad and replaced. On the way home punched it to get on highway and the car starts shuttering just like it did before. pull over, restart the car and everything fine. Same thing happened again this am when wife went to work. I would think if it was another coil it would not reset. I noticed on the repair bill they mention possible faulty inlet and exhaust cam sensors but they didnt replace. Those were also replaced last summer but not oem. Would it be more apt to be sensors instead of coils? BTW moritz wants me to bring it back but will charge me another $130 diag. fee. Anyone else having coil probs due to excessive Texas heat this summer?