when hot wont start

my 95 xj has this funny problem when the engine get hot and even more so when its hot out side. it wil turn over like it wants to start but i wont kick. i have to wait about 5 to 10 minutes usually before its cool enough and will start up again. the last owner told me that he had to replace his coolant temp sensor every summer to fix the problem. i think the problem is that the last owner is running a 180* thermostat. i figure the engine get hot and after being shut off teh computer reads that the temp io way to high and wont let it start. so far i have picked up a new stock thermostat 190* i think and a new temp sensor. the weird thing is that it only happens once in a while (every couple days) and it has only happened once in a day. it also usually only happens after being run for a short period of time. today it happened after being run for 15 mins. the time it took me to get home form school. got home shut it off for 5 mins and went out again and it would not start. took about ten mins of trying to get it to start.

any ideas?