Laptop runs for 20 minutes and starts to fail. If

Check engine light on? Need codes. Could be a sensor failing when at temp, head gasket, intake, etc

This could be a sign that your laptop is overheating. If you touch the laptop while it is running & you find it too hot, make sure that the fan is running properly & that the air ways are not blocked.
You can blow compressed air into the cooling vents of the fan. If you notice clouds of dust coming out, then it might be a good idea to disassemble the laptop, clean the fan & air ways, & reassemble it back. If the fan has failed & is no longer running, it might need to be replaced.

This could be a sign that your laptop is overheating. If you touch the laptop while it is running & you find it too hot, make sure that the fan is running properly & that the air ways are not blocked.
You can blow compressed air into the cooling vents of the fan. If you notice clouds of dust coming out, then it might be a good idea to disassemble the laptop, clean the fan & air ways, & reassemble it back. If the fan has failed & is no longer running, it might need to be replaced.

This could be a sign that your laptop is overheating. If you touch the laptop while it is running & you find it too hot, make sure that the fan is running properly & that the air ways are not blocked.
You can blow compressed air into the cooling vents of the fan. If you notice clouds of dust coming out, then it might be a good idea to disassemble the laptop, clean the fan & air ways, & reassemble it back. If the fan has failed & is no longer running, it might need to be replaced.

If none of this solves the problem, or is not the case, then you might have a bad motherboard

This could be a sign that your laptop is overheating. If you touch the laptop while it is running & you find it too hot, make sure that the fan is running properly & that the air ways are not blocked.
You can blow compressed air into the cooling vents of the fan. If you notice clouds of dust coming out, then it might be a good idea to disassemble the laptop, clean the fan & air ways, & reassemble it back. If the fan has failed & is no longer running, it might need to be replaced.

If none of this solves the problem, or is not the case, then you might have a bad motherboard.

This could be a sign that your laptop is overheating. If you touch the laptop while it is running & you find it too hot, make sure that the fan is running properly & that the air ways are not blocked.
You can blow compressed air into the cooling vents of the fan. If you notice clouds of dust coming out, then it might be a good idea to disassemble the laptop, clean the fan & air ways, & reassemble it back. If the fan has failed & is no longer running, it might need to be replaced.

If none of this solves the problem, or is not the case, then you might have a bad motherboard.

This could be a sign that your laptop is overheating. If you touch the laptop while it is running & you find it too hot, make sure that the fan is running properly & that the air ways are not blocked.
You can blow compressed air into the cooling vents of the fan. If you notice clouds of dust coming out, then it might be a good idea to disassemble the laptop, clean the fan & air ways, & reassemble it back. If the fan has failed & is no longer running, it might need to be replaced.

If none of this solves the problem, or is not the case, then you might have a bad motherboard.

replace the battery . battery has its own life time and after that it needs to be replaced . so do it.

Have you checked for spark & fuel when it won't start. ? First thing I'd do is confirm if both are good.